CSS Notes For Professionals - intermediate level CSS learning course.
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An external CSS stylesheet can be applied to any number of HTML documents by placing a <link> element in each HTML document.
The attribute rel of the <link> tag has to be set to "stylesheet", and the href attribute to the relative or absolute path to the stylesheet. While using relative URL paths is generally considered good practice, absolute paths can be used, too. In HTML5 the type attribute can be omitted.
It is recommended that the <link> tag be placed in the HTML file’s <head> tag so that the styles are loaded before the elements they style. Otherwise, users will see a flash of unstyled content.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
<h1>Hello world!</h1>
<p>I ♥ CSS</p>
</body>
</html>
h1 {
color: green;
text-decoration: underline;
}
p {
font-size: 25px;
font-family: 'Trebuchet MS', sans-serif;
}
Make sure you include the correct path to your CSS file in the href. If
the CSS file is in the same folder as your HTML file then no path is
required (like the example above) but if it’s saved in a folder, then
specify it like this;
href="foldername/style.css"
<link rel="stylesheet" type="text/css" href= "foldername/style.css">
External stylesheets are considered the best way to handle your CSS. There's a very simple reason for this: when you're managing a site of, say, 100 pages, all controlled by a single stylesheet, and you want to change your link colors from blue to green, it's a lot easier to make the change in your CSS file and let the changes "cascade" throughout all 100 pages than it is to go into 100 separate pages and make the same change 100 times. Again, if you want to completely change the look of your website, you only need to update this one file.
You can load as many CSS files in your HTML page as needed.
<link rel="stylesheet" type="text/css" href="main.css"> <link rel="stylesheet" type="text/css" href="override.css">
CSS rules are applied with some basic rules, and order does matter. For example, if you have a main.css file with some code in it:
p.green { color: #00ff00; }
All your paragraphs with the 'green' class will be written in light green, but you can override this with another .css file just by including it after main.css. You can have override.css with the following code follow main.css, for example:
p.green { color: #006600; }
Now all your paragraphs with the 'green' class will be written in darker green rather than light green.
Other principles apply, such as the '!important' rule, specificity, and inheritance.
When someone first visits your website, their browser downloads the HTML of the current page plus the linked CSS file. Then when they navigate to another page, their browser only needs to download the HTML of that page; the CSS file is cached, so it does not need to be downloaded again. Since browsers cache the external stylesheet, your pages load faster.
CSS enclosed in <style></style> tags within an HTML document function like an external stylesheet, except that it lives in the HTML document it styles instead of in a separate file, and therefore can only be applied to the document in which it lives. Note that this element must be inside the <head> element for HTML validation (though it will work in all current <head> browsers if placed in body).
<head>
<style>
h1 {
color: green;
text-decoration: underline;
}
p {
font-size: 25px;
font-family: 'Trebuchet MS', sans-serif;
}
</style>
</head>
<body>
<h1>Hello world!</h1>
<p>I ♥ CSS</p>
</body>
The @import CSS at-rule is used to import style rules from other style sheets. These rules must precede all other types of rules, except @charset rules; as it is not a nested statement, @import cannot be used inside conditional group at-rules @import.
You can use @import rule in the following ways:
<style>
@import url('/css/styles.css');
</style>
The following line imports a CSS file named additional-styles.css in the root directory into the CSS file in which it appears:
@import '/additional-styles.css';
Importing external CSS is also possible. A common use case are font files:
@import 'https://fonts.googleapis.com/css?family=Lato';
An optional second argument to @import rule is a list of media queries:
@import '/print-styles.css' print; @import url('landscape.css') screen and (orientation: landscape);
Use inline styles to apply styling to a specific element. Note that this is not optimal. Placing style rules in a <style> tag or external CSS file is encouraged in order to maintain a distinction between content and presentation.
Inline styles override any CSS in a <style> tag or external style sheet. While this can be useful in some circumstances, this fact more often than not reduces a project's maintainability.
The styles in the following example apply directly to the elements to which they are attached.
<h1 style="color: green; text-decoration: underline;">Hello world!</h1> <p style="font-size: 25px; font-family: 'Trebuchet MS';">I ♥ CSS</p>
Inline styles are generally the safest way to ensure rendering compatibility across various email clients, programs and devices, but can be time-consuming to write and a bit challenging to manage.
It's possible to add, remove or change CSS property values with JavaScript through an element's style property.
var el = document.getElementById("element");
el.style.opacity = 0.5;
el.style.fontFamily = 'sans-serif';
Note that style properties are named in lower camel case style. In the example you see that the css property fontfamily becomes fontFamily in javascript.
As an alternative to working directly on elements, you can create a <style> or <link> element in JavaScript and append it to the <body> or <head> of the HTML document.
Modifying CSS properties with jQuery is even simpler.
$('#element').css('margin', '5px');
$('#element').css({ margin:"5px", padding:"10px", color:"black" });
jQuery includes two ways to change css rules that have hyphens in them (i.e. font-size). You can put them in quotes or camel-case the style rule name.
$('.example-class').css({ "background-color": "blue", fontSize: "10px" });
There are three different properties for styling list-items: list-style-type, list-style-image, and list-style position, which should be declared in that order. The default values are disc, outside, and none, respectively. Each property can be declared separately, or using the list-style shorthand property.
list-style-type defines the shape or type of bullet point used for each list-item.
Some of the acceptable values for list-style-type:
(For an exhaustive list, see the W3C specification WIKI).
To use square bullet points for each list-item, for example, you would use the following property-value pair:
li {
list-style-type: square;
}
The list-style-image property determines whether the list-item icon is set with an image, and accepts a value of none or a URL that points to an image.
li {
list-style-image: url (images/bullet.png);
}
The list-style-position property defines where to position the list-item marker, and it accepts one of two values: "inside" or "outside".
li {
list-style-position: inside;
}
Some properties can take multiple values, collectively known as a property list.
/* Two values in this property list */
span {
text-shadow: yellow 0 0 3px, green 4px 4px 10px;
}
/* Alternate Formatting */
span {
text-shadow:
yellow 0 0 3px,
green 4px 4px 10px;
}
When you group CSS selectors, you apply the same styles to several different elements without repeating the styles in your style sheet. Use a comma to separate multiple grouped selectors.
div, p {color: blue }
So the blue color applies to all <div> elements and all <p> elements. Without the comma only <p> elements that are a child of a <div> would be red.
This also applies to all types of selectors.
p, .blue, #first, div span{ color : blue }
A CSS rule consists of a selector (e.g. h1) and declaration block ({}).
h1 {}
/* This is a CSS comment */
div {
color: red; /* This is a 2nd CSS comment */
}
/*
This
is
a multiline
CSS
comment
*/
div {
color: red;
}
CSS selectors identify specific HTML elements as targets for CSS styles. This topic covers how CSS selectors target HTML elements. Selectors use a wide range of over 50 selection methods offered by the CSS language, including elements, classes, IDs, pseudo-elements and pseudo-classes, and patterns.
| Selector | Description |
|---|---|
| * | Universal selector (all elements) |
| div | Tag selector (all <div> elements) |
| .blue | Class selector (all elements with class blue) |
| .blue.red | All elements with class blue and red (a type of Compound selector) |
| #headline | ID selector (the element with “id” attribute set to headline) |
| :pseudo-class | All Elements with pseudo-class |
| ::pseudo-element | Element that matches pseudo-element |
| :lang(en) | Element that matches :lang declaration, for example <span lang="en"> |
| div > p | child selector |
Note: The value of an ID must be unique in a web page. It is a violation of the HTML standard to use the value of an ID more than once in the same document tree.
A complete list of selectors can be found in the CSS Selectors Level 3 specification.
Attribute selectors can be used with various types of operators that change the selection criteria accordingly. They select an element using the presence of a given attribute or attribute value.
| Selector(1) | Matched element | Selects elements… |
|---|---|---|
| [attr] | <div attr> | With attribute attr. |
| [attr='val'] | <div attr="val"> | Where attribute attr has value val. |
| [attr~='val'] | <div attr="val val2 val3"> | Where val appears in the whitespace-separated list of attr. |
| [attr^='val'] | <div attr="val1 val2"> | Where attr’s value begins with val. |
| [attr$='val'] | <div attr="sth aval"> | Where attr’s value ends with val. |
| [attr*='val'] | <div attr="somevalhere"> | Where attr contains val anywhere. |
| [attr|='val'] | <div attr="val-sth etc"> | Where attr’s value is exactly val, or starts with val and immediately followed by - (U+002D). |
| [attr='val' i] | <div attr="val"> | Where attr has val, ignoring val's letter casing. |
Selects elements with the given attribute.
div[data-color] {
color: red;
}
<div data-color="red">This will be red</div>
<div data-color="green">This will be red</div>
<div data-background="red">This will NOT be red</div>
[attribute="value"]
Selects elements with the given attribute and value.
div[data-color="red"] { color: red; } <div data-color="red">This will be red</div> <div data-color="green">This will be red</div> <div data-background="red">This will NOT be red</div>
[attribute="value"]
Selects elements with the given attribute and value where the given attribute contains the given value anywhere (as a substring).
[class*= "foo"] {
color: red;
}
<div class="foo-123">This will be red</div>
<div class="foo123">This will be red</div>
<div class="bar123foo">This will be red</div>
<div class="barfooo123">This will be red</div>
<div class="barfo0">This will NOT be red</div>
[attribute~="value"]
Selects elements with the given attribute and value where the given value appears in a whitespace-separated list.
[class~="color-red"] {
color: red;
}
<div class="color-red foo-bar the-div">This will be red</div>
<div class="color-blue" foo-bar the-div">
This will NOT be red</div>
[attribute^="value"]
Selects elements with the given attribute and value where the given attribute begins with the value.
[class^="foo-"] {
color: red;
}
<div class="foobar-file">This will be red</div>
<div class="foobar-file">This will be red</div>
<div class="foobar-input">This will NOT be red</div>
[attribute$="value"]
Selects elements with the given attribute and value where the given attribute ends with the given value.
[class$="file"] {
color: red;
}
<div class="foobar-file">This will be red</div>
<div class="foobar-file">This will be red</div>
<div class="foobar-input">This will NOT be red</div>
[attribute|="value"]
Selects elements with a given attribute and value where the attribute's value can be represented as Value, VALUE, vAlUe or any other case-sensitive possibility.
[lang|="EN" i] {
color: red;
}
<div lang="EN-us">This will be red</div>
<div lang="EN-gb">This will be red</div>
<div lang="PT-pt">This will NOT be red</div>
[attribute="value" i]
Selects elements with a given attribute and value where the attribute's value can be represented as Value, VALUE, vAlUe or any other case-insensitive possibility.
[lang|="EN"] {
color: red;
}
<div lang="EN-us">This will be red</div>
<div lang="EN-gb">This will be red</div>
<div lang="PT-pt">This will NOT be red</div>
Live Demo (jsBin)
Same as class selector and pseudoclass.
*[type=checkbox] // 0-1-0
Note that this means an attribute selector can be used to select an element by its ID at a lower level of specificity than if it was selected with an ID selector: [id=“my-ID”] targets the same element as #my-ID but with lower specificity.
See the Syntax Section for more details.
| Selector | Description |
|---|---|
| div span | Descendant selector (all <span>s that are descendants of a <div>) |
| div > span | Child selector (all <span>s that are direct child of a <div>) |
| a ~ span | General Sibling selector (all <span>s that are siblings after an <a>) |
| a + span | Adjacent Sibling selector (all <span> that are immediately after an <a>) |
Note: Sibling selectors target elements that come after them in the source document. CSS, by its nature (it cascades), cannot target previous or parent elements. However, using the flex order property, a previous sibling selector can be simulated on visual media.
A descendant combinator, represented by at least one space character (), selects elements that are a descendant of the defined element. This combinator selects all descendants of the element (from child elements on down).
div p {
color: red;
}
<div>
<p>My text is red</p>
<section>
<p>My text is red</p>
</section>
</div>
<p>My text is not red</p>
In the above example, the first two <p> elements are selected since they are both descendants of the <div>.
The child (>) combinator is used to select elements that are children, or direct descendants, of the specified element.
div > p {
color: red;
}
<div>
<p>My text is red</p>
<section>
<p>My text is not red</p>
</section>
</div>
The above CSS selects only the first <p> element, as it is the only paragraph directly descended from a <div>.
The second <p> element is not selected because it is not a direct child of the <div>.
The adjacent sibling (+) combinator selects a sibling element that immediate follows a specified element.
p + p {
color: #ff0000; /* red */
}
<p>My text is not red</p>
<p>My text is red</p>
<p>My text is red</p>
<hr>
<p>My text is not red</p>
The above example selects only those <p> elements which are directly preceded by another <p> element.
The general sibling (~) combinator selects all siblings that follow the specified element.
p ~ p color: red; } <p>My text is not red</p> <p>My text is red</p> <hr> <h1>And now a title</h1> <p>My text is red</p>
The above example selects all <p> elements that are preceded by another <p> element, whether or not they are immediately adjacent.
Pseudo-classes are keywords which allow selection based on information that lies outside of the document tree that cannot be expressed by other selectors or combinators. This information can be associate to a certain state (state and dynamicpseudo-classes), to locations (structural and target pseudo-classes), to negations of the former (negation pseudo-class) or the languages (lang pseudo-class). Examples include whether or not a link has been followed (:visited), the mouse is over an element (:hover), a checkbox is checked (:checked), etc.
selector:pseudo-class {
property: VALUE;
}
| Name | Description |
|---|---|
| :active | Applies to any element being activated (i.e. clicked) by the user. |
| :any | Allows you to build sets of related selectors by creating groups that included items will match. This is an alternative to repeating an entire selector. |
| :target | Selects the current active #news element (clicked on a URL containing that anchor name). |
| :checked | Applies to radio, checkbox, or option elements that are checked or toggled into an “on” state. |
| :default | Represents any user interface element that is the default among a group of similar elements. |
| :disabled | Applies to any UI element which is in a disabled state. |
| :empty | Applies to any element which has no children. |
| :enabled | Applies to any UI element which is in an enabled state. |
| :first | Used in conjunction with @page rule, this selects the first page in a printed document. |
| :first-child | Represents any element that is the first child element of its parent. |
| :first-of-type | Applies when an element is the first of the selected element type inside its parent. This may or may not be the first-child. |
| :focus | Applies to any element which has the user’s focus. This can be given by the user’s keyboard, mouse events, or other forms of input. |
| :focus-within | Can be used to highlight a whole section when one element inside it is focused. It matches any element that the :focus pseudo-class matches or that has a descendant focused. |
| :full-screen | Applies to any element displayed in full-screen mode. It selects the whole stack of elements and not just the top level element. |
| :hover | Applies to any element being hovered by the user's pointing device, but not activated. |
| :indeterminate | Applies radio or checkbox UI elements which are neither checked nor unchecked, but are in an indeterminate state. This can be due to an element’s attribute or DOM manipulation. |
| :in-range | The :in-range CSS pseudo-class matches when an element has its value attribute inside the specified range limitations for this element. It allows the page to give a feedback that the value currently defined using the elements is inside the range limits. |
| :invalid | Applies to <input> elements whose values are invalid according to the type specified in the type= attribute. |
| :lang | Applies to any element who's wrapping <body> element has a properly designated lang= attribute. For the pseudo-class to be valid, it must contain a valid two or three language code. |
| :last-child | Represents any element that is the last child element of its parent. |
| :last-of-type | Applies when an element is the last of the selected element type inside its parent. This may or may not be the last-child. |
| :left | Used in conjunction with the @page rule, this selects all the left pages in a printed document. |
| :link | Applies to any links which haven't been visited by the user. |
| :not() | Applies to all elements which do not match the value passed to :not(p) or :not(.class-name) for example. It must have a value to be valid and it can only contain one selector. However, youi can chain multiple together. |
| :nth-child | Applies when an element is the n-th element of its parent, where an can be an integer, a mathematical expression (e.g n+3) or the keywords odd or even. |
| :nth-of-type | Applies when an eleent is the n-th element of its parent of the same element type, where n can be an integer, a mathematical expression (e.g n+3) or the keywords odd or even. |
| :only-child | The :only-child CSS pseudo-class represents any element which is the only child of a parent. This is the same as :first-child:last-child or :nth-child(1):nth-last-child(1), but with a lower specificity. |
| :optional | The :optional CSS pseudo-class represents any element that does not have the required attribute set on it. This allows forms to easily indicate optional fields and to style them accordingly. |
| :out-of-range | The :out-of-range CSS pseudo-class matches when an element has its value attribute outside the specified range limitations for this element. It allows the page to give a feedback that the value currently defined using the element is outside the range limits. A value can be outside of a range if it is either smaller or larger than maximum and minimum set values. |
| :placeholder-shown | Experimental: Applies to any form element currently displaying placeholder text. |
| :read-only | Applies to any element which is not editable by the user. |
| :read-write | Applies to any element that is editable by a user, such as <input> elements. |
| :right | Used in conjunction with the @page rule, this selects all the right pages in a printed document. |
| :root | Matches the root element of a tree representing the document. |
| :scope | CSS pseudo-class matches the elements that are a reference point for selectors to match against. |
| :target | Selects the current active #news element (clicked on a URL containing that anchor name). |
| :visited | Applies to any links which have been visited by the user. |
The :visited pseudo-class can’t be used for most styling in a lot of modern browsers anymore because it’s a security hole. See this link for reference.
"The :nth-child(an+b) CSS pseudo-class matches an element that has an+b-1 siblings before it in the document tree, for a given positive or zero value for n" - [MDN :nth-child]
| pseudo-selector | 1 2 3 4 5 6 7 8 9 10 |
|---|---|
| :first-child | ✔ |
| :nth-child (3) | ✔ |
| :nth-child (n+3) | ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ |
| :nth-child (3n) | ✔ ✔ ✔ |
| :nth-child (3n+1) | ✔ ✔ ✔ ✔ |
| :nth-child (-n+3) | ✔ ✔ ✔ |
| :nth-child (odd) | ✔ ✔ ✔ ✔ ✔ |
| :nth-child (even) | ✔ ✔ ✔ ✔ ✔ |
| :last-child | ✔ |
| :nth-last-child(3) | ✔ |
The class name selector select all elements with the targeted class name. For example, the class name .warning would select the following <div> element:
<div class="warning"> <p>This would be some warning copy.</p> </div>
You can also combine class names to target elements more specifically. Let's build on the example above to showcase a more complicated class selection.
.important {
color: orange;
}
.warning {
color: #0000ff; /* blue */
}
.warning .important {
color: #de1205; /* red */
}
<div class="warning"> <p>This would be some warning copy.</p> </div> <div class="important warning"> <p class="important">This is some really important warning copy.</p> </div>
In this example, all elements with the .warning class will have a blue text color, elements with the .important class with have an orange text color, and all elements that have both the .important and .warning class name will have a red text color.
Notice that within the CSS, the .warning.important declaration did not have any spaces between the two class names. This means it will only find elements which contain both class names warning and important in their class attribute. Those class names could be in any order on the element.
If a space was included between the two classes in the CSS declaration, it would only select elements that have parent elements with a .warning class names and child elements with .important class names.
This trick helps you select an element using the ID as a value for an attribute selector to avoid the high specificity of the ID selector.
<div id="element">. . .</div>
#element { . . . } /* High specificity will override many selectors */
[id="element"] { . . .} /* Low specificity, can be overridden easily */
The :last-of-type selects the element that is the last child, of a particular type, of its parent. In the example below, the css selects the last paragraph and the last heading h1.
p: last-of-type {
background: #C5CAE9;
}
h1: last-of-type {
background: #CDDC39;
}
<div class="container">
<p>First paragraph</p>
<p>Second paragraph</p>
<p>Last paragraph</p>
<h1>Heading 1</h1>
<h2>First Heading 2</h2>
<h2>Last heading 2</h2>
</div>
<image left justified> Demo (jsFiddle).
<style>
input:in-range {
border: 1px solid blue;
}
</style>
<input type="number" min="10" max="20" value="15">
<p>The border for this value will be blue</p>
The :in-range CSS pseudo-class matches when an element has its value attribute inside the specified range limitations for this element. It allows the page to give a feedback that the value currently defined using the element is inside the range limits.[:in-range].
The following selector matches all <input> elements in an HTML document that are not disabled and don't have the class .example:
<form> Phone: <input type="tel" class="example"> E-mail: <input type="email" disabled="disabled"> Password: <input type="password"> </form>
input:not([disabled]):not(.example){
background-color: #ccc;
}
The :not() pseudo-class will also support comma-separated selectors in Selectors Level 4:
input:not([disabled]):not(.example){
background-color: #ccc;
}
See background syntax here:
<h3>Background is blue if the input is focused.</p>
<div>
<input type="text">
</div>
div {
height: 80px;
}
input {
margin: 30px;
}
div:focus-within {
background-color: #1565C0;
}
With the ~ selector, you can easily implement a global accessible boolean without using JavaScript.
To the very beginning of your document, add as much booleans as you want with a unique id and the hidden attribute set:
<input type="checkbox" dis="sidebarShown" hidden />
<input type="checkbox" dis="darkThemeUsed" hidden />
<!-- here begins actual content, for example: -->
<div id="container">
<div id="sider">
<!-- Menu, Search, ... -->
</div>
<!-- Some more content ... -->
</div>
<div id="footer">
<!-- ... -->
</div>
You can toggle the boolean by adding a label with the for attribute set:
<label for="sidebarShown">Show/Hide the sidebar!</label>
The normal selector (like .color-red) specifies the default properties. They can be overridden by following true / false selectors:
/* true: */ <checkbox>:checked ∽ [sibling of checkbox & parent of target] <target> /* false: */ <checkbox>:not(:checked) ~ [sibling of checkbox & parent of target] <target>
Note that <checkbox>, [sibling …] and <target> should be replaced by the proper selectors. [sibling …] can be a specific selector, (often if you’re lazy) simply * or nothing if the target is already a sibling of the checkbox.
#sidebarShown:checked ~ #container #sidebar {
margin-left: 300px;
}
#darkThemeUsed:checked ~ #container,
#darkThemeUsed:checked ~ #footer {
background: #333;
}
See this Fiddle for an implementation of these global booleans.
ID selectors select DOM elements with the targeted ID. To select an element by a specific ID in CSS, the # prefix is used.
For example, the following HTML div element…
<div id="exampleID"> <p>Example</p> </div>
…can be selected by #exampleID in CSS as shown below:
#exampleID {
width: 20px;
}
Note: The HTML specs do not allow multiple elements with the same ID.
<input type="range"></input>
| Effect | Pseudo Selector |
|---|---|
| Thumb | input[type=range]::-webkit-slider-thumb, input[type=range]::-moz-range-thumb, |
| input[type=range]::-ms-thumb | |
| Track | input[type=range]::-webkit-slider-runnable-track, input[type=range]::-moz-range-track, |
| input[type=range]::-ms-track | |
| OnFocus | input[type=range]:focus |
| Lower part of | input[type=range]::-moz-range-progress, input[type=range]::-mx-fill-lower(not possible |
| the track | in WebKit browsers currently -JS needed) |
The :only-child CSS pseudo-class represents any element which is the only child of its parent.
<div> <p>This paragraph is the only child of the div, it will have the color blue</p> </div> <div> <p>This paragraph is one of the two children of the div</p> <p>This paragraph is one of the two children of its parent</p> </div>
p:only-child {
color: blue;
}
The above example selects the <p> element that is the unique child from its parent, in this case a <div>.
With CSS you can set colors, gradients, and images as the background of an element.
It is possible to specify various combinations of images, colors, and gradients, and adjust the size, positioning, and repetition (among others) of these.
The background-color property sets the background color of an element using a color value or through keywords, such as transparent, inherit or initial.
This can be applied to all elements, and ::first-letter/::first-line pseudo-elements.
Colors in CSS can be specified by different methods.
div {
background-color: #de1205; /* red */
}
<div>This will have a red background</div>
Hex code is used to denote RGB components of a color in base-16 hexadecimal notation. #ff0000, for example, is bright red, where the red component of the color is 256 bits (ff) and the corresponding green and blue portions of the color is 0 (00).
If both values in each of the three RGB pairings (R, G, and B) are the same, then the color code can be shortened into three characters (the first digit of each pairing). #ff0000 can be shortened to #f00, and #ffffff can be shortened to #fff.
Hex notation is case-insensitive.
body {
background-color: #de1205; /* red */
}
.main {
background-color: #00f; /* blue */
}
Another way to declare a color is to use RGB or RGBa.
RGB stands for Red, Green and Blue, and requires of three separate values between 0 and 255, put between brackets, that correspond with the decimal color values for respectively red, green and blue.
RGBa allows you to add an additional alpha parameter between 0.0 and 1.0 to define opacity.
header {
background-color: rgb(0, 0, 0); /* black */
}
footer {
background-color: rgba(0, 0, 0, 0.5); /* black with 50% opacity */
}
Another way to declare a color is to use HSL or HSLa and is similar to RGB and RGBa.
HSL stands for hue, saturation, and lightness, and is also often called HLS:
HSLa allows you to add an additional alpha parameter between 0.0 and 1.0 to define opacity.
li a {
background-color: hsl(120, 100%, 50%); /* green */
}
#p1 {
background-color: hsla(120, 100%, 50%, .3); /* green with 30% opacity */
}
The following statements are all equivalent:
body {
background: red;
background-image: url (partiallytransparentimage.png);
}
body {
background-color: red;
background-image: url (partiallytransparentimage.png);
}
body {
background-image: url(partiallytransparentimage.png);
background-color: red;
}
body {
background: red url (partiallytransparentimage.png);
}
They will all lead to the red color being shown underneath the image, where the parts of the image are transparent, or the image is not showing (perhaps as a result of background-repeat).
Note that the following is not equivalent:
body {
background-image: url(partiallytransparentimage.png);
background: #ff0000; /* red */
}
Here, the value of background overrides your background-image.
For more info on the background property, see Background Shorthand.
Gradients are new image types, added in CSS3. As an image, gradients are set with the background-image property, or the background shorthand.
There are two types of gradient functions, linear and radial. Each type has a non-repeating variant and a repeating variant:
A linear-gradient has the following syntax:
background: linear-gradient( <direction>?, <color-stop-1>, <color-stop-2>, …);
| Value | Meaning |
|---|---|
| <direction> | Could be an argument like to top, to bottom, to right or to left; or an angle as 0deg, |
| 90deg… . The angle starts from top and rotates clockwise. Can be specified in deg, grad, rad, | |
| or turn. If omitted, the gradient flows from top to bottom. | |
| <color-stop-list> | List of colors, optionally followed each one by a percentage or length to display it at. For |
| example, yellow 10%, rgba(0,0,0,.5) 40px, #fff 100%… |
For example, this creates a linear gradient that starts from the right and transitions from red to blue.
.linear-gradient {
background: linear-gradient (to left, red, blue); /* you can also use 270deg */
}
You can create a diagonal gradient by declaring both a horizontal and vertical starting position.
.diagonal-linear-gradient {
background: linear-gradient (to left top, red, yellow 10%);
}
It is possible to specify any number of color stops in a gradient by separating them with commas. The following examples will create a gradient with 8 color stops;
.linear-gradient-rainbow {
background: linear-gradient(to left, red, orange, yellow, green, blue, indigo, violet);
}
.radial-gradient-simple {
background: radial-gradient(red, blue);
}
.radial-gradient {
background: radial-gradient(circle farthest-corner at top left, red, blue);
}
| Value | Meaning |
|---|---|
| circle | Shape of gradient. Values are circle or ellipse, default is ellipse. |
| farthest-corner | Keywords describing how big the ending shape must be. Values are closes-side, |
| farthest-side, closest-corner, farthest-corner. | |
| top left | Sets the position of the gradient center, in the same way as background-position. |
Repeating gradient functions take the same arguments as the above examples, but tile the gradient across the background of the element.
.bullseye {
background: repeating-radial-gradient(red, red 10%, white 10%, white 20%);
}
.warning {
background: repeating-linear-gradient(-45deg, yellow, yellow 10%, black 10%, black 20%);
}
| Value | Meaning |
|---|---|
| -45deg | Angle unit. The angle starts from the top and rotates clockwise. Can be specified in deg, grad, rad, or turn. |
| to left | Direction of gradient, default is to bottom. Syntax: to [y-axis(top or bottom)] [x-axis(left OR |
| right)] ie to top right. | |
| yellow 10% | Color, optionally followed by a percentage or length to display it at. Repeated two or more times. |
Note that HEX, RGB, RGBa, HSL, and HSLa color codes may be used instead of color names. Color names were used for the sake of illustration. Also note that the radial-gradient syntax is much more complex than linear-gradient, and a simplified version is shown here. For a full explanation and specs, see the MDN Docs.
The background-image property is used to specify a background image to be applied to all matched elements. By default, this image is tiled to cover the entire element, excluding margin.
.myClass {
background-image: url ('/path/to/image.jpg');
}
To use multiple images as background-image, define comma separated url().
.myClass {
background-image: url ('/path/to/image.jpg'),
url ('/path/to/image2.jpg');
}
The images will stack according to their order with the first declared image on top of the others and so on.
| Value | Result |
|---|---|
| url ('/path/to/image.jpg') | Specify background image's path(s) or an image resource specified with data URI |
| schema (apostrophes can be omitted), separate multiples by comma. | |
| none | No backgound image. |
| initial | Default value. |
| inherit | Inherit parent’s value. |
The following attributes are very useful and almost essential;
The background property can be used to set one or more background related properties:
| Value | Description |
|---|---|
| background-image | Background image to use. |
| background-color | Background color to apply. |
| background-position | Background image's position. |
| background-size | Background image's size. |
| background-repeat | How to repeat background image. |
| background-origin | How the background is positioned (ignored when |
| background-attachment is fixed). | |
| background-clip | How the background is painted relative to the |
| content-box, border-box, or the padding-box. | |
| background-attachment | How the background image behaves, whether it |
| scrolls along with its containing block or has a | |
| fixed position within the viewport. | |
| initial | Sets the property value to default. |
| inherit | Inherits property value from parent. |
The order of the values does not matter and every value is optional.
The syntax of the background shorthand declaration is:
background: [<background-image>]
[<background-color>]
[<background-position>]/[<background-size>]
[<background-repeat>] [<background-origin>]
[<background-clip>] [<background-attachment>]
[<initial|inherit>];
background: #ff0000;
Simply setting a background-color with the red value.
background: border-box red;
Setting a background-clip to border-box and a background-color to red.
background: no-repeat center url("somepng.jpg");
Sets a background-repeat to no-repeat, background-origin to center and a background-image to an image.
background: url('pattern.png') green;
In this example, the background-color of the element would be set to green with pattern.png, if it is available, overlayed on the colour, repeating as often as necessary to fill the element. If pattern.png includes any transparency then the green colour will be visible behind it;
background: #000000 url("picture.png") top left / 600px auto no-repeat;
In this example we have a black background with an image 'picture.png' on top, the image does not repeat in either axis and is positioned in the top left corner. The / after the position is to be able to include the size of the background image which in this case is set as 600px width and auto for the height. This example could work well with a feature image that can fade into a solid colour;
NOTE: Use of the shorthand background property resets all previously set background property values, even if a value is not given. If you wish only to modify a background property value previously set, use a longhand property instead.
The
Demo (background-size) property enables
one to control the scaling of the background-image. It takes up to two values, which
determine the scale/size of the resulting image in vertical and and horizontal direction.
If the property is missing, its deemed auto in both width and height.
auto will
keep the image's aspect ratio, if it can be determined. The height is optional and can
be considered auto. Therefore, on a 256 px × 256 px image, all the following
background-size settings would yield an image with height and width of 50 px:
background-size: 50px; background-size: 50px auto; /* same as above */ background-size: auto 50px; background-size: 50px 50px;
So if we started with the following picture (which has the mentioned size of 256 px × 256 px);
We'll end up with a 50 px × 50 px on the user's screen, contained in the background of our element:
One can also use percentage values to scale the image with respect of the element. The following example would yield a 200 px × 133 px drawn image:
#withbackground {
background-image: url(to/some/background.png);
background-size: 100% 66%;
width:200px;
height: 200px;
padding: 0;
margin: 0;
}
The behaviour depends on the Demo (background-origin).
The last example in the previos section lost its original aspect ratio. The circle got into an ellipse, the square into a rectangle, the triangle into another triangle.
The length or percentage approach isn't flexible enough to keep the aspect ratio at all times. auto doesn't help, since you might not know which dimension of your element will be larger. However, to cover certain areas with an image (and correct aspect ratio) completely or to contain an image with correct aspect ratio completely in a background area, the values, contain and cover provide the additional functionality.
Sorry for the bad pun, but we're going to use a picture of the day by Biswarup Ganguly for demonstration. Lets say that this is your screen, and the gray area is outside of your visible screen. For demonstration, we’re going to assume a 16 x 9 ratio.
We want to use the aforementioned picture of the day as a background. However, we cropped the image to 4x3 for some reason. We could set the background-size property to some fixed length, but we will focus on contain and cover. Note that I also assume that we didn't mangle the width and/or height of body.
contain Scale the image, while preserving its intrinsic aspect ratio (if any), to the largest size such that both its width and its height can fit inside the background positioning area.
This makes sure that the background image is always completely contained in the background positioning area, however, there could be some empty space filled with your background-color in this case:
cover Scale the image, while preserving its intrinsic aspect ratio (if any), to the smallest size suck that both its width and height can completely cover the background positioning area.
This makes sure that the background image is covering everything. There will be no visible background-color, however depending on the screen's ratio a great part of your image could be cut off:
div > div {
background-image: url(http://i.stack.imgur.com/r5CAq.jpg);
background-repeat: no-repeat;
background-position: center center;
background-color: #ccc;
border: 1px solid;
width: 20em;
height: 10em;
}
div .contain {
background-size: contain;
}
div .cover {
background-size: cover;
}
/*********************************
Additional styles for the explanation boxes
*********************************/
div > div {
margin: 0 1ex 1ex 0;
float: left;
}
div + div {
clear: both;
border-top: 1px dashed silver;
padding-top: 1ex;
}
div > div::after {
background-color: #000;
color: #fefefe;
margin: 1ex;
padding: 1ex;
opacity: 0.8;
display: block;
width: 10ex;
font-size: 0.7em;
content: attr(class);
}
<div>
<div class="contain"></div>
<p>Note the grey background. The image does not cover the whole region,
but it's fully<
<em>contained</em>.
</p>
</div>
<div>
<div class="cover"></div>
<p>Note the ducks/geese at the bottom of the image. Most of the water is
cut, as well as a part of the sky. You don't see the complete
image anymore, but neither do you see any background color;
the image<em>covers</em> all of the <code><div></code>.</p>
</div>
The background-position property is used to specify the starting position for a background image or gradient.
.myClass {
background-image: url('path/to/image.jpg');
background-position: 50% 50%;
}
The position is set using an X and Y co-ordinate and be set using any of the units used within CSS.
| Unit | Description |
|---|---|
| value% value% | A percentage for the horizontal offset is relative to (width of |
| background positioning area - width of background image). | |
| A percentage for the vertical offset is relative to | |
| (height of background positioning area - height of background image) | |
| The size of the image is the size given by background-size. | |
| valuepx valuepx | Offsets background image by a length given in pixels relative to the |
| top left of the background valuepx valuepx positioning area |
Units in CSS can be specified by different methods (see here).
In addition to the shorthand property above, one can also use the longhand background properties backgroundposition-x and background-position-y. These allow you to control the x or y positions separately.
NOTE: This is supported in all browsers except Firefox (versions 31-48)[2]. Firefox 49, to be released September 2016, will support these properties. Until then, there is a Firefox hack within this Stack Overflow answer.
The background-origin property specifies where the background image is positioned.
Note: If the background-attachment property is set to fixed, this property has no effect.
Possible values:
.example {
width: 300px;
border: 20px solid black;
padding: 50px;
background: url (https://static.pexels.com/photos/6440/magazines-desk-work-workspace-medium.jpg);
background-repeat: no-repeat;
}
.example1 {}
.example2 { background-origin: border-box; }
.example3 { background-origin: content-box;}
<p>No background-origin (padding-box is default):</p> <div class="example example1"><h2> <h2>Lorem Ipsum Dolor</h2><p> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat.</p> <p>Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat.</p> </div> <p>background-origin: border-box:</p> <div class="example example2"> <h2>Lorem Ipsum Dolor</h2> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat.</p> <p>Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat.</p> </div> <p>background-origin: content-box:</p> <div class="example example3"> <h2>Lorem Ipsum Dolor</h2> <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat.</p> <p>Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat.</p> </div>
More:
In CSS3, we can stack multiple background in the same element.
#mydiv {
background-image: url(img_1.png), /* top image */
url (img_2.png), /* middle image */
url (img_3.png); /* bottom image */
background-position: right bottom,
left top,
right top;
background-repeat: no-repeat,
repeat,
no-repeat;
}
Images will be stacked atop one another with the first background on top and the last background in the back. img_1 will be on top, the img_2 and img_3 is on bottom.
We can also use background shorthand property for this:
#mydiv {
background: url(img_1.png) right bottom no-repeat,
url(img_2.png) left top repeat,
url(img_3.png) right top no-repeat;
}
We can also stack images and gradients:
#mydiv {
background: url(image.png) right bottom no-repeat,
linear-gradient (to bottom, #fff 0%, #000 100%);
}
The background-attachment property sets whether a background image is fixed or scrolls with the rest of the page.
body {
background-image: url('img.jpg');
background-attachment: fixed;
}
| Value | Description |
|---|---|
| scroll | The background scrolls along with the element. This is default. |
| fixed | The background is fixed with regard to the viewport. |
| local | The background scrolls along with the element's contents. |
| initial | Sets this property to its default value. |
| inherit | Inherits this property from its parent element. |
The default behaviour, when the body is scrolled the background scrolls with it:
body {
background-image: url('image.jpg');
background-attachment: scroll;
}
The background image will be fixed and will not move when the body is scrolled:
body {
background-image: url('image.jpg');
background-attachment: fixed;
}
The background image of the div will scroll when the contents of the div is scrolled.
div {
background-image: url('image.jpg');
background-attachment: local;
}
Definition and Usage: The background-clip property specifies the painting area of the background.
Default value: border-box
.example {
width:300px;
border:20px solid black;
padding:50px;
background:url (https://static.pexels.com/photos/6440/magazines-desk-work-workspace-medium.jpg);
background-repeat: no-repeat;
}
.example1 {}
.example2 { background-origin: border-box; }
.example3 { background-origin: content-box; }
<p>No background-origin (padding-box is default):</p>
<div class="example example1">
<h2>Lorem Ipsum Dolor</h2>
<p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod
tincidunt ut laoreet dolore magna aliquam erat volutpat.</p>
<p>Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut
aliquip ex ea commodo consequat.</p>
</div>
<p>background-origin: border-box:</p>
<div class="example example2">
<h2>Lorem Ipsum Dolor</h2>
<p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod
tincidunt ut laoreet dolore magna aliquam erat volutpat.</p>
<p>Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut
aliquip ex ea commodo consequat.</p>
</div>
<p>background-origin: content-box:</p>
<div class="example example3">
<h2>Lorem Ipsum Dolor</h2>
<p>There once was a man fron Sash. His balls were made of glass
When he rubbed them together, he made stormy weather.
And lightning struck out of his ass.</p>
<p>And more goes here, as well. It beats Latin. I don't know Latin so better
for me the end.</p>
</div>
The background-repeat property sets if/how a background image will be repeated.
By default, a background-image is repeated both vertically and horizontally.
div {
background-image: url ("img.jpg");
background-repeat: repeat-y;
}
Here’s how a background-repeat: repeat-y looks like:
.my-div {
width:300px;
height:200px;
background-size:100%;
background-repeat:no-repeat;
background-image:linear-gradient (to right, black 0% ,white 100%),
url('https://static.pexels.com/photos/54624/strawberry-fruit-red-sweet-54624-medium.jpeg');
background-blend-mode:saturation;
}
<div class="my-div">Lorem ipsum</div>
See result here: Demo (jsFiddle).
CSS Syntax: background-blend-mode: normal | multiply | screen | overlay | darken | lighten | color-dodge | saturation | color | luminosity;
If you set opacity on an element it will affect all its child elements. To set an opacity just on the background of an element you will have to use RGBA colors. Following example will have a black background with 0.6 opacity.
/* Fallback for web browsers that don't support RGBa */ background-color:rgb (0, 0, 0); /* RGBa with 0.6 opacity */ background-color:rgba (0, 0, 0, 0.6); /* For IE 5.5 - 7 */ filter: progid:DXImageTransform.Microsoft.gradient(startColorstr = #99000000, endColorstr = #99000000); /* For IE 8 */ −ms-filter: "progid:DXImageTransform.Microsoft.gradient(startColorstr=#99000000, endColorstr=#99000000)";
<div class="container"> <img src="http://lorempixel.com/400/200" /> </div>
html, body, .container {
height:100%;
}
.container {
display: flex;
justify-content: center; /* horizontal center */
}
img {
align-self:center; /* vertical center */
}
<img src = "http://lorempixel.com/400/200" />
html, body {
height:100%;
}
body {
display:flex;
justify-content:center; /* horizontal center */
align-items:center; /* vertical center */
}
See Dynamic Vertical and Horizontal Centering under the Flexbox documentation for more details on flexbox and what the styles mean.
Flexbox is supported by all major browsers, except IE versions before 10.
Some recent browser versions, such as Safari 8 and IE10, require vendor prefixes.
For a quick way to generate prefixes there is Autoprefixer, a third-party tool.
For older shitty browsers (like IE 8 & 9) a Polyfill is available.
For a more detailed look at flexbox browser support, see this answer.
CSS transforms are based on the size of the elements so if you don't know how tall or wide your element is, you can position it absolutely 50% from the top and left of a relative container and translate it by 50% left and upwards to center it vertically and horizontally.
Keep in mind that with this technique, the element could end up being rendered at a non-integer pixel boundary, making it look blurry. See this answer in Stack Overflow for a workaround.
<div class="container"> <div class="element"></div> </div>
.container {
position: relative;
}
.element {
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}
The transform property needs prefixes to be supported by older browsers. Prefixes are needed for Chrome<=35, Safari<=8, Opera<=22, Android Browser<=4.4.4, and IE9. CSS transforms are not supported by IE8 and older versions.
Here is a common transform declaration for the previous example:
-webkit-transform: translate(-50%, -50%); /* Chrome, Safari, Opera, Android */
-ms-transform: translate(-50%, -50%); /* IE 9 */
transform: translate(-50%, -50%);
For more information see canIuse.
Objects can be centered by using if they are block elements and have a defined width.
<div class="containerDiv">
<div id="centeredDiv"></div>
</div>
<div class="containerDiv">
<p id="centeredParagraph">This is a centered paragraph.</p>
</div>
<div class="containerDiv">
<img id="centeredImage"
src="https://i.kinja-img.com/gawker-media/image/upload/s--c7Q9b4Eh−-/c_scale,fl_progressive,q_80,w_800/qqyvc3bkpyl3mfhr8all.jpg" />
</div>
.containerDiv {
width: 100%;
height: 100px;
padding-bottom: 40px;
}
#centeredDiv {
margin: 0 auto;
width: 200px;
height: 100px;
border: 1px solid #000;
}
#centeredParagraph {
width: 200px;
margin: 0 auto;
}
#centeredImage {
display: block;
width: 200px;
margin: 0 auto;
}
JSFiddle example: Centering objects with margin: 0 auto Demo (jsFiddle).
The most common and easiest type of centering is that of lines of text in an element. CSS has the rule text-align: center for this purpose:
<p>Lorem ipsum</p>
p {
text-align: center;
}
This does not work for centering entire block elements. text-align controls only alignment of inline content like text in its parent block element.
See more about text-align in Typography section.
Working in old browsers (IE >= 8)
Automatic margins, paired with values of zero for the left and right or top and bottom offsets, will center an absolutely positioned elements within its parent.
<div class="parent"> <img class="center" src="http://lorempixel.com/400/200/"/> </div>
.parent {
position: relative;
height: 500px;
}
.center {
position: absolute;
margin: auto;
top: 0;
right: 0;
bottom: 0;
left: 0;
}
Elements that don't have their own implicit width and height like images do, will need those values defined.
Other resources: Absolute Centering in CSS (CodePen).
The calc() function is the part of a new syntax in CSS3 in which you can calculate (mathematically) what size/position your element occupies by using a variety of values like pixels, percentages, etc. Note: Whenever you use this function, always take care of the space between two values calc(100% - 80px).
.center {
position: absolute;
height: 50px;
width: 50px;
background: #ff0000; /* red */
top: calc (50% − 50px/2); /* height divided by 2 */
left: calc (50% − 50px / 2); /* width divided by 2 */
}
<div class="center"></div>
You can also use line-height to center vertically a single line of text inside a container:
div {
height: 200px;
line-height: 200px;
}
That's quite ugly, but can be useful inside an <input /> element. The line-height property works only when the text to be centered spans a single line. If the text wraps into multiple lines, the resulting output won't be centered.
Use these 3 lines to vertical align practically everything. Just make sure the div/image you apply the code to has a parent with a height.
div .vertical {
position: relative;
top: 50%;
transform: translateY(-50%);
}
<div class="vertical">Vertical aligned text!</div>
We will see how to center content based on the height of a near element.
Compatibility: IE8+, all other modern browsers.
<div class="content">
<div class="position-container">
<div class="thumb">
<img src="http://lorempixel.com/400/200/">
</div>
<div class="details">
<p class="banner-title">text 1</p>
<p class="banner-text">content content content content content content content content
content content content content content content</p>
<button class="btn">button</button>
</div>
</div>
</div>
.content * {
box-sizing: border-box;
}
.content .position-container {
display: table;
}
.content .details {
display: table-cell;
vertical-align: middle;
width: 33.333333%;
padding: 30px;
font-size: 17px;
text-align: center;
}
.content .thumb {
width: 100%;
}
.content .thumb img {
width: 100%;
}
The main points are the 3; .thumb, .details and .position-container containers:
This technique works even when the container's dimensions are unknown.
Set up a "ghost" element inside the container to be centered that is 100% height, then use vertical-align: middle on both that and the element to be centered.
/* This parent can be any width and height */
.block {
text-align: center;
/* May want to do this if there is risk the container may be
narrower than the element inside */
white-space: nowrap;
}
/* The ghost element */
.block: before {
content: '';
display: inline-block;
height: 100%;
vertical-align: middle;
/* There is a gap between ghost element and .centered,
caused by space character rendered. Could be eliminated by
nudging .centered (nudge distance depends on font family),
or by zeroing font-size in .parent and resetting it back
(probably to 1rem) in .centered. */
margin-right: -0.25em;
}
/* The element to be centered, can also be of any width and height */
.centered {
display: inline-block;
vertical-align: middle;
width: 300px;
white-space: normal; /* Resetting inherited nowrap behavior */
}
<div class="block"> div class="centered"></div> </div>
The following technique allows you to add your content to an HTML element and center it both horizontally and vertically without worrying about its height or width.
<div class="outer-container">
<div class="inner-container">
<div class="centered-content">
You can put anything here!
</div>
</div>
</div>
body {
margin: 0;
}
.outer-container {
position: absolute;
display: table;
width: 100%; /* This could be ANY width */
height: 100%; /* This could be ANY height */
background: #ccc;
}
.inner-container {
display: table-cell;
vertical-align: middle;
text-align: center;
}
.centered-content {
display: inline-block;
text-align: left;
background: #fff;
padding: 20px;
border: 1px solid #000;
}
See also this jsFiddle!
<div class="wrap"> <img src="http://lorempixel.com/400/200/"/> </div>
.wrap {
height: 50px; /* max image height */
width: 100px;
border: 1px solid blue;
text-align: center;
}
.wrap:before {
content:"";
display: inline-block;
height: 100%;
vertical-align: middle;
width: 1px;
}
img {
vertical-align: middle;
}
If the size of your content is fixed, you can use absolute positioning to 50% with margin that reduces half of your content's width and height:
<div class="center"> Center vertically and horizontally </div>
.center {
position: absolute;
background: #ccc;
left: 50%;
width: 150px;
margin-left: -75px; /* width * -0.5 */
top: 50%;
height: 200px;
margin-top: -100px; /* height * -0.5 */
}
You can center the element horizontally even if you don't know the height of the content:
<div class="center"> Center only horizontally </div>
.center {
position: absolute;
background: #ccc;
left: 50%;
width: 150px;
margin-left: -75px; /* width * -0.5 */
}
You can center the element vertically if you know the element's height:
<div class="center"> Center only vertically </div>
.center {
position: absolute;
background: #ccc;
top:50%;
height: 200px;
margin-top: -100px; /* width * -0.5 */
}
Applying css intuitively doesn't produce the desired results because;
For widest browser support, a workaround with helper elements:
<div class="vcenter−-container"> <div class="vcenter−-helper"> <div class="vcenter−-content"> <!-- stuff --> </div> </div> </div>
.vcenter −- container {
display: table;
height: 100%;
position: absolute;
overflow: hidden;
width: 100%;
}
.vcenter −- helper {
display: table-cell;
vertical-align: middle;
}
.vcenter −- content {
margin: 0 auto;
width: 200px;
}
Demo (jsFiddle) vertical align dynamic height elements from original question.
One could easily center a child element using table display property.
<div class="wrapper"> <div class="parent"> <div class="child"></div> </div> </div>
.wrapper {
display: table;
vertical-align: center;
width: 200px;
height: 200px;
background-color: #9e9e9e;
}
.parent {
display: table-cell;
vertical-align: middle;
text-align: center;
}
.child {
display: inline-block;
vertical-align: middle;
text-align: center;
width: 100px;
height: 100px;
background-color: teal;
}
| Parameter | Detail |
|---|---|
| content-box | Width and height of the element only includes content area. |
| padding-box | Width and height of the element includes content and padding. |
| border-box | Width and height of the element includes content, padding and border. |
| initial | Sets the box model to its default state. |
| inherit | Inherits the box model of the parent element. |
The browser creates a rectangle for each element in the HTML document. The Box Model describes how the padding, border, and margin are added to the content to create this rectangle.
Diagram from CSS2.2 Working Draft Demo.
The perimeter of each of the four areas is called an edge. Each edge defines a box.
div {
border: 5px solid #ff0000;
margin: 50px;
padding: 20px;
}
This CSS styles all div elements to have a top, right, bottom and left border of 5px in width; a top, right, bottom and left margin of 50px; and a top, right, bottom, and left padding of 20px. Ignoring content, our generated box will look like this:
Now lets give our element a sibling with the same style. The browser looks at the Box Model of both elements to work out where in relation to the previous element's content the new element should be positioned:
The content of each of element is separated by a 150px gap, but the two elements' boxes touch each other.
If we then modify our first element to have no right margin, the right margin edge would be in the same position as the right border edge, and our two elements would now look like this:
The default box model (content-box) can be counter-intuitive, since the width / height for an element will not represent its actual width or height on screen as soon as you start adding padding and border styles to the element.
The following example demonstrates this potential issue with content-box:
textarea {
width: 100%;
padding: 3px;
box-sizing: content-box; /* default value */
}
Since the padding will be added to the width of the textarea, the resulting element is a textarea that is wider than 100%.
Fortunately, CSS allows us to change the box model with the box-sizing property for an element. There are three different values for the property available:
To solve the textarea problem above, you could just change the box-sizing property to padding-box or borderbox. border-box is most commonly used.
textarea {
width: 100%;
padding: 3px;
box-sizing: border-box;
}
To apply a specific box model to every element on the page, use the following snippet:
html {
box-sizing: border-box;
}
*, *:before, *:after {
box-sizing: inherit;
}
In this coding box-sizing: border-box; is not directly applied to *, so you can easily overwrite this property on individual elements.
| Parameter | Details |
|---|---|
| 0 | set margin to none. |
| auto | used for centering, by evenly setting values on each side units. |
| units (e.g. px) | see parameter section in Units for a list of valid units. |
| inherit | inherit margin value from parent element. |
| initial | restore to initial value. |
When two margins are touching each other vertically, they are collapsed. When two margins touch horizontally, they do not collapse.
Consider the following styles and markup:
div {
margin: 10px;
}
<div>
some content
</div>
<div>
some more content
</div>
They will be 10px apart since vertical margins collapse over one and other. (The spacing will not be the sum of two margins.)
Consider the following styles and markup:
span {
margin: 10px;
}
<span>some</span><span>content</span>
They will be 20px apart since horizontal margins don't collapse over one and other. (The spacing will be the sum of two margins.)
.top {
margin: 10px;
}
.bottom {
margin: 15px;
}
<div class = "top">
some content
</div>
<div class = "bottom">
some more content
</div>
These elements will be spaced 15px apart vertically. The margins overlap as much as they can, but the larger margin will determine the spacing between the elements.
.outer-top {
margin: 10px;
}
.inner-top {
margin: 15px;
}
.outer-bottom {
margin: 20px;
}
.inner-bottom {
margin: 25px;
}
<div class ="outer-top">
<div class="inner-top">
some content
</div>
</div>
<div class="outer-bottom">
<div class="inner-bottom">
some more content
</div>
</div>
What will be the spacing between the two texts? (hover to see answer)
The spacing will be 25px. Since all four margins are touching each other, they will collapse, thus using the largest margin of the four.
Now, what about if we add some borders to the markup above.
div {
border: 1px solid #ff0000;
}
What will be the spacing between the two texts? (hover to see answer)
The spacing will be 59px! Now only the margins of .outer-top and .outer-bottom touch each other, and are the only collapsed margins. The remaining margins are separated by the borders. So we have 1px + 10px + 1px + 15px + 20px + 1px + 25px + 1px. (The 1px's are the borders...)
<h1>Title</h1> <div> <p>Paragraph</p> </div>
h1 {
margin: 0;
background: #cff;
}
div {
margin: 50px 0 0 0;
background: #cfc;
}
p {
margin: 25px 0 0 0;
background: #cf9;
}
In the example above, only the largest margin applies. You may have expected that the paragraph would be located 60px from the h1 (since the div element has a margin-top of 40px and the p has a 20px margin-top). This does not happen because the margins collapse together to form one margin.
CSS allows you to specify a given side to apply margin to. The four properties provided for this purpose are:
The following code would apply a margin of 30 pixels to the left side of the selected div. View Result.
<div id="myDiv"></div>
#myDiv {
margin-left: 30px;
height: 40px;
width: 40px;
background-color: #ff0000;
}
| Parameter | Details |
|---|---|
| margin-left | The direction in which the margin should be applied. |
| 30px | The width of the margin. |
The standard margin property can be expanded to specify differing widths to each side of the selected elements. The syntax for doing this is as follows:
margin: <top> <right> <bottom> <left>;
The following example applies a zero-width margin to the top of the div, a 10px margin to the right side, a 50px margin to the left side, and a 100px margin to the left side. View Result.
<div id="myDiv"></div>
#myDiv {
margin: 0 10px 50px 100px;
height: 40px;
width: 40px;
background-color: #ff0000;
}
p {
margin: 1px; /* 1px margin in all directions */
/* equal to: */
margin: 1px 1px;
/* equal to: */
margin: 1px 1px 1px;
/* equal to: */
margin: 1px 1px 1px 1px;
}
Another exapmle:
p {
margin: 10px 15px; /* 10px margin-top & bottom And 15px margin-right & left */
/* equal to: */
margin: 10px 15px 10px 15px;
/* equal to: */
margin: 10px 15px 10px;
/* margin left will be calculated from the margin right value (=15px) */
}
As long as the element is a block, and it has an explicitly set width value, margins can be used to center block elements on a page horizontally.
We add a width value that is lower than the width of the window and the auto property of margin then distributes the remaining space to the left and the right:
#myDiv {
width:80%;
margin:0 auto;
}
In the example above we use the shorthand margin declaration to first set 0 to the top and bottom margin values (although this could be any value) and then we use auto to let the browser allocate the space automatically to the left and right margin values.
In the example above, the #myDiv element is set to 80% width which leaves use 20% leftover. The browser distributes this value to the remaining sides so:
(100% - 80%) / 2 = 10%
It is obvious to assume that the percentage value of margin to margin-left and margin-right would be relative to its parent element.
.parent {
width : 500px;
height: 300px;
}
.child {
width : 100px;
height: 100px;
margin-left: 10%; /* (parentWidth * 10/100) => 50px */
}
But that is not the case, when comes to margin-top and margin-bottom. Both these properties, in percentages, aren't relative to the height of the parent container but to the width of the parent container.
So,
.parent {
width : 500px;
height: 300px;
}
.child {
width : 100px;
height: 100px;
margin-left: 10%; /* (parentWidth * 10/100) => 50px */
margin-top: 20%; /* (parentWidth * 20/100) => 100px */
}
Margin is one of a few CSS properties that can be set to negative values. This property can be used to overlap elements without absolute positioning.
div {
display: inline;
}
#over {
margin-left: -20px;
}
<div>Base div</div>
<div id="over">Overlapping div</div>
The padding property sets the padding space on all sides of an element. The padding area is the space between the content of the element and its border. Negative values are not allowed.
To save adding padding to each side individually (using padding-top, padding-left etc) can you write it as a shorthand, as below:
<style>
.myDiv {
padding: 25px 50px 75px 100px; /* top right bottom left; */
}
</style>
<div class="myDiv"></div>
<style>
.myDiv {
padding: 25px 50px 75px; /* top left/right bottom */
}
</style>
<div class="myDiv"></div>
<style>
.myDiv {
padding: 25px 50px; /* top/bottom left/right */
}
</style>
<div class="myDiv"></div>
<style>
.myDiv {
padding: 25px; /* top/right/bottom/left */
}
</style>
<div class="myDiv"></div>
The padding property sets the padding space on all sides of an element. The padding area is the space between the content of the element and its border. Negative values are not allowed.
You can specify a side individually:
The following code would add a padding of 5px to the top of the div:
<style>
.myClass {
padding-top: 5px;
}
</style>
<div class="myClass"></div>
The border-radius property allows you to change the shape of the basic box model.
Every corner of an element can have up to two values, for the vertical and horizontal radius of that corner (for a maximum of 8 values).
The first set of values defines the horizontal radius. The optional second set of values, preceded by a ‘/’ , defines the vertical radius. If only one set of values is supplied, it is used for both the vertical and horizontal radius.
border-radius: 10px 5% / 20px 25em 30px 35em;
The 10px is the horizontal radius of the top-left-and-bottom-right. And the 5% is the horizontal radius of the topright-and-bottom-left. The other four values after '/' are the vertical radii for top-left, top-right, bottom-right and bottom-left.
As with many CSS properties, shorthands can be used for any or all possible values. You can therefore specify anything from one to eight values. The following shorthand allows you to set the horizontal and vertical radius of every corner to the same value:
<div class='box'></div>
.box {
width: 250px;
height: 250px;
background-color: black;
border-radius: 10px;
}
Border-radius is most commonly used to convert box elements into circles. By setting the border-radius to half of the length of a square element, a circular element is created:
.circle {
width: 200px;
height: 200px;
border-radius: 100px;
}
Because border-radius accepts percentages, it is common to use 50% to avoid manually calculating the borderradius value:
.circle {
width: 150px;
height: 150px;
border-radius: 50%;
}
If the width and height properties are not equal, the resulting shape will be an oval rather than a circle.
Browser specific border-radius example:
-webkit-border-top-right-radius: 4px; -webkit-border-bottom-right-radius: 4px; -webkit-border-bottom-left-radius: 0; -webkit-border-top-left-radius: 0; -moz-border-radius-topright: 4px; -moz-border-radius-bottomright: 4px; -moz-border-radius-bottomleft: 0; -moz-border-radius-topleft: 0; border-top-right-radius: 4px; border-bottom-right-radius: 4px; border-bottom-left-radius: 0; border-top-left-radius: 0;
The border-style property sets the style of an element's border. This property can have from one to four values (for every side of the element one value.)
border-style: dotted; border-style: dotted solid double dashed;
border-style can also have the values none and hidden. They have the same effect, except hidden works for <table> elements. In a <table> with multiple borders, none has the lowest priority (meaning in a conflict, the border would show), and hidden has the highest priority (meaning in a conflict, the border would not show).
.div1 {
border: 3px solid black;
outline: 6px solid blue;
width: 100px;
height: 100px;
margin: 20px;
}
.div2 {
border: 5px solid green;
box-shadow: 0px 0px 0px 4px #000;
width: 100px;
height: 100px;
margin: 20px;
}
.div3 {
position: relative;
border: 5px solid #000;
width: 100px;
height: 100px;
margin: 20px;
}
.div3:before {
content: " ";
position: absolute;
border: 5px solid blue;
z-index: −1;
top: 5px;
left: 5px;
right: 5px;
bottom: 5px;
}
In most cases you want to define several border properties (border-width, border-style and border-color) for all sides of an element.
border-width: 1px; border-style: solid; border-color: #000;
border: 1px solid #000;
These shorthands are also available for every side of an element: border-top, border-left, border-right and border-bottom. So you can do:
border-top: 2px double #aaaaaa;
The border-collapse property applies only to tables (and elements displayed as or inlinetable) and sets whether the table borders are collapsed into a single border or detached as in standard HTML.
table {
border-collapse: separate; /* default */
border-spacing: 2px; /* Only works if border-collapse is separate */
}
Also see Tables - border-collapse documentation entry
With the border-image property you have the possibility to set an image to be used instead of normal border styles.
Consider the following example wheras border.png is a image of 90x90 pixels:
border-image: url("border.png") 30 stretch;
The image will be split into nine regions with 30x30 pixels. The edges will be used as the corners of the border while the side will be used in between. If the element is higher / wider than 30px this part of the image will be stretched. The middle part of the image defaults to be transparent.
.bordered {
border-image: linear-gradient(to right, red 20%, green 20%, green 40%, blue 40%, blue 60%, maroon
60%, maroon 80%, chocolate 80%); /* gradient with required colors */
border-image-slice: 1;
}
<div class='bordered'>Border on all sides</div>
The above example would produce a border that comprises of 5 different colors. The colors are defined through a linear-gradient (you can find more information about gradients in the docs). You can find more information about border-image-slice property in the border-image example in same page.
You'd have noticed that the left border has only a single color (the start color of the gradient) while the right border also has only a single color (the gradient's end color). This is because of the way that border image property works. It is as though the gradient is applied to the entire box and then the colors are masked from the padding and content areas, thus making it look as though only the border has the gradient.
Which border(s) have a single color is dependant on the gradient definition. If the gradient is a gradient, the left border would be the start color of the gradient and right border would be the end color. If it was a to bottom gradient the top border would be the gradient's start color and bottom border would be end color. Below is the output of a bottom 5 colored gradient.
If the border is required only on specific sides of the element then the border-width property can be used just like with any other normal border. For example, adding the below code would produce a border only on the top of the element.
border-width: 5px 0px 0px 0px;
Note that, any element that has border-image property won't respect the border-radius (that is the border won't curve). This is based on the below statement in the spec:
A box's backgrounds, but not its border-image, are clipped to the appropriate curve (as determined by ‘background-clip’).
The border-[left|right|top|bottom] property is used to add a border to a specific side of an element.
For example if you wanted to add a border to the left side of an element, you could do:
#element {
border-left: 1px solid black;
}
| Parameter | Details |
|---|---|
| dotted | dotted outline |
| dashed | dashed outline |
| solid | solid outline |
| double | double outline |
| groove | 3D grooved outline, depends on the outline-color value |
| ridge | 3D ridged outline, depends on the outline-color value |
| inset | 3D inset outline, depends on the outline-color value |
| outset | 3D outset outline, depends on the outline-color value |
| none | no outline |
| hidden | hidden outline |
Outline is a line that goes around the element, outside of the border. In contrast to border, outlines do not take any space in the box model. So adding an outline to an element does not affect the position of the element or other elements.
In addition, outlines can be non-rectangular in some browsers. This can happen if outline is applied on a span element that has text with different font-size properties inside it. Unlike borders, outlines cannot have rounded corners.
The essential parts of outline are outline-color, outline-style and outline-width.
The definition of an outline is equivalent to the definition of a border:
An outline is a line around an element. It is displayed around the margin of the element. However, it is different from the border property.
outline: 1px solid black;
The outline-style property is used to set the style of the outline of an element.
p {
border: 1px solid black;
outline-color: blue;
line-height: 30px;
}
.p1 {
outline-style: dotted;
}
.p2 {
outline-style: dashed;
}
.p3 {
outline-style: solid;
}
.p4 {
outline-style: double;
}
.p5 {
outline-style: groove;
}
.p6 {
outline-style: ridge;
}
.p7 {
outline-style: inset;
}
.p8 {
outline-style: outset;
}
<p class="p1">A dotted outline</p> <p class="p2">A dashed outline</p> <p class="p3">A solid outline</p> <p class="p4">A double outline</p> <p class="p5">A groove outline</p> <p class="p6">A ridge outline</p> <p class="p7"> An inset outline</p> <p class="p8"> An outset outline</p>
| Overflow Value | Details |
|---|---|
| visible | Shows all overflowing content outside the element. |
| scroll | Hides the overflowing content and adds a scroll bar. |
| hidden | Hides the overflowing content, both scroll bars disappear and the page becomes fixed. |
| auto | Same as scroll if content overflows, but doesn't add scroll bar if content fits. |
| inherit | Inherit's the parent element's value for this property. |
overflow-wrap tells a browser that it can break a line of text inside a targeted element onto multiple lines in an otherwise unbreakable place. Helpful in preventing an long string of text causing layout problems due to overflowing it's container.
div {
width: 100px;
outline: 1px dashed #bbb;
}
#div1 {
overflow-wrap:normal;
}
#div2 {
overflow-wrap:break-word;
}
<div id="div1">
<strong>#div1</strong>: Small words are displayed normally, but a long word like <span
style="red;">supercalifragilisticexpialidocious</span> is too long so it will overflow past the
edge of the line-break
</div>
<div id="div2">
<strong>#div2</strong: Small words are displayed normally, but a long word like <span
style="red;">supercalifragilisticexpialidocious</span> will be split at the line break and continue
on the next line.
</div>
| overflow-wrap – Value | Details |
|---|---|
| normal | Lets a word overflow if it is longer than the line. |
| break-word | Will split a word into multiple lines, if necessary. |
| inherit | Inherits the parent element's value for this property. |
These two properties work in a similar fashion as the overflow property and accept the same values. The overflow-x parameter works only on the x or left-to-right axis. The overflow-y works on the y or top-to-bottom axis.
<div id="div-x"> If this div is too small to display its contents, the content to the left and right will be clipped. </div> <div id="div-y"> If this div is too small to display its contents, the content to the top and bottom will be clipped. </div>
div {
width: 200px;
height: 200px;
}
#div-x {
overflow-x: hidden;
}
#div-y {
overflow-y: hidden;
}
<div> This div is too small to display its contents to display the effects of the overflow property. </div>
div {
width: 100px;
height: 100px;
overflow: scroll;
}
The content above is clipped in a 100px by 100px box, with scrolling available to view overflowing content.
Most desktop browsers will display both horizontal and vertical scrollbars, whether or not any content is clipped. This can avoid problems with scrollbars appearing and disappearing in a dynamic environment. Printers may print overflowing content.
<div> Even if this div is too small to display its contents, the content is not clipped. </div>
div {
width: 50px;
height: 50px;
overflow: visible;
}
Content is not clipped and will be rendered outside the content box if it exceeds its container size.
Using the overflow property with a value different to visible will create a new block formatting context. This is useful for aligning a block element next to a floated element.
img {
float: left;
margin-right: 10px;
}
div {
overflow: hidden; /* creates block formatting context */
}
<img src="http://placehold.it/100x100">
<div>
<p>Lorem ipsum dolor sit amet, cum no paulo mollis pertinacia.</p>
<p>Ad case omnis nam, mutat deseruisse persequeris eos ad, in tollit debitis sea.</p>
</div>
This example shows how paragraphs within a div with the overflow property set will interact with a floated image.
| Parameter | Details |
|---|---|
| mediatype | (Optional) This is the type of media. Could be anything in the range of all to screen. |
| not | (Optional) Doesn't apply the CSS for this particular media type and applies for everything |
| else. | |
| media feature | Logic to identify use case for CSS. Options outlined below. |
| Media Feature | Details |
|---|---|
| aspect-ratio | Describes the aspect ratio of the targeted display area of the output device. |
| color | Indicates the number of bits per color component of the output device. If the device is not a |
| color device, this value is zero. | |
| color-index | Indicates the number of entries in the color look-up table for the output device. |
| grid | Determines whether the output device is a grid device or a bitmap device. |
| height | The height media feature describes the height of the output device's rendering surface. |
| max-width | CSS will not apply on a screen width wider than specified. |
| min-width | CSS will not apply on a screen width narrower than specified. |
| max-height | CSS will not apply on a screen height taller than specified. |
| min-height | CSS will not apply on a screen height shorter than specified. |
| monochrome | Indicates the number of bits per pixel on a monochrome (greyscale) device. |
| orientation | CSS will only display if device is using specified orientation. See remarks for more details. |
| resolution | Indicates the resolution (pixel density) of the output device. |
| scan | Describes the scanning process of television output devices. |
| width | The width media feature describes the width of the rendering surface of the output device |
| (such as the width of the document window, or the width of the page box on a printer). |
| Deprecated Features | Details |
|---|---|
| device-aspect-ratio | Deprecated CSS will only display on devices whose height/width. |
| ratio matches the specified ratio. This is an adeprecated feature and is not guaranteed to work. | |
| max-device-width | Deprecated Same as max-width but measures the physical screen width, rather than the |
| display width of the browser. | |
| min-device-width | Deprecated Same as min-width but measures the physical screen width, rather than the |
| display width of the browser. | |
| max-device-height | Deprecated Same as max-height but measures the physical screen width, rather than the |
| display width of the browser. | |
| min-device-height | Deprecated Same as min-height but measures the physical screen width, rather than the |
| display width of the browser. |
Media queries allow one to apply CSS rules based on the type of device / media (e.g. screen, print or handheld) called media type, additional aspects of the device are described with media features such as the availability of color or viewport dimensions.
@media [...] {
/* One or more CSS rules to apply when the query is satisfied */
}
@media print {
/* One or more CSS rules to apply when the query is satisfied */
}
@media screen and (max-width: 600px) {
/* One or more CSS rules to apply when the query is satisfied */
}
@media (orientation: portrait) {
/* One or more CSS rules to apply when the query is satisfied */
}
@media screen and (min-width: 720px) {
body {
background-color: skyblue;
}
}
The above media query specifies two conditions:
If these conditions are met, the styles inside the media query will be active, and the background color of the page will be sky blue.
Media queries are applied dynamically. If on page load the conditions specified in the media query are met, the CSS will be applied, but will be immediately disabled should the conditions cease to be met. Conversely, if the conditions are initially not met, the CSS will not be applied until the specified conditions are met.
In our example, if the user's view port width is initially greater than 720 pixels, but the user shrinks the browser's width, the background color will cease to be sky blue as soon as the user has resized the view port to less than 720 pixels in width.
Media queries have an optional mediatype parameter. This parameter is placed directly after the @media declaration( @media mediatype mediatype), for example:
@media print {
html {
background-color: white;
}
}
The above CSS code will give the DOM HTML element a white background color when being printed.
The mediatype parameter has an optional not or only prefix that will apply the styles to everything except the specified mediatype or only the specified media type, respectively. For example, the following code example will apply the style to every media type except print.
@media not print {
html {
background-color: green;
}
}
And the same way, for just showing it only on the screen, this can be used:
@media only screen {
.fadeInEffects {
display: block;
}
}
The list of mediatype can be understood better with the following table:
| Media Type | Description |
|---|---|
| all | Apply to all devices. |
| screen | Default computers. |
| Printers in general. Used to style print-versions of websites. | |
| handheld | PDA's, cellphones and hand-held devices with a small screen. |
| projection | For projected presentation, for example projectors. |
| aural | Speech Systems. |
| braille | Braille tactile devices. |
| embossed | Paged braille printers. |
| tv | Television-type devices. |
| tty | Devices with a fixed-pitch character grid. Terminals, portables. |
Although this works only for WebKit based browsers, this is helpful:
/* ----------- Non-Retina Screens ----------- */ @media screen and (min-width: 1200px) and (max-width: 1600px) and (−webkit-min-device-pixel-ratio: 1) { } /* ----------- Retina Screens ----------- */ @media screen and (min-width: 1200px) and (max-width: 1600px) and (−webkit-min-device-pixel-ratio: 2) and (min-resolution: 192dpi) { }
There are two types of pixels in the display. One is the logical pixels and the other is the physical pixels. Mostly, the physical pixels always stay the same, because it is the same for all the display devices. The logical pixels change based on the resolution of the devices to display higher quality pixels. The device pixel ratio is the ratio between physical pixels and logical pixels. For instance, the MacBook Pro Retina, iPhone 4 and above report a device pixel ratio of 2, because the physical linear resolution is double the logical resolution.
The reason why this works only with WebKit based browsers is because of:
When we are using "width" with media queries it is important to set the meta tag correctly. Basic meta tag looks like this and it needs to be put inside the <head> tag.
<meta name="viewport" content="width=device-width,initial-scale=1">
Based on MDN's definition "width" is
The width media feature describes the width of the rendering surface of the output device (such as the width of the document window, or the width of the page box on a printer).
What does that mean?
View-port is the width of the device itself. If your screen resolution says the resolution is 1280 x 720, your view-port width is "1280px".
More often many devices allocate different pixel amount to display one pixel. For an example iPhone 6 Plus has 1242 x 2208 resolution. But the actual viewport-width and viewport-height is 414 x 736. That means 3 pixels are used to create 1 pixel.
But if you did not set the meta tag correctly it will try to show your webpage with its native resolution which results in a zoomed out view (smaller texts and images).
Often times, responsive web design involves media queries, which are CSS blocks that are only executed if a condition is satisfied. This is useful for responsive web design because you can use media queries to specify different CSS styles for the mobile version of your website versus the desktop version.
@media only screen and (min-width: 300px) and (max-width: 767px) { .site-title { font-size: 80%; } /* Styles in this block are only applied if the screen size is at least 300px wide, but no more than 767px */ } @media only screen and (min-width: 768px) and (max-width:1023px) { .site-title { font-size: 90%; } /* Styles in this block are only applied if the screen size is at least 768px wide, but no more than 1023px */ } @media only screen and (min-width: 1024px) { .site-title { font-size: 120%; } /* Styles in this block are only applied if the screen size is over 1024px wide. */ }
<link rel="stylesheet" media="min-width: 600px" href="example.css" />
This stylesheet is still downloaded but is applied only on devices with screen width larger than 600px.
Media queries are not supported at all in IE8 and below (MS managment sucks).
To add support for IE8, you could use one of several JS solutions. For example, Respond can be added to add media query support for IE8 only With the following code:
<!−-[if lt IE 9]> <script src="respond.min.js"> </script> <![endif]−->
CSS Mediaqueries is another library that does the same thing. The code for adding that library to your HTML would be identical:
<!−-[if lt IE 9]> <script src="css3-mediaqueries.js"> </script> <![endif]−->
If you don't like a JS based solution, you should also consider adding an IE<9 only stylesheet where you adjust your styling specific to IE<9. For that, you should add the following HTML to your code:
<!−-[if lt IE 9]> <link rel="stylesheet" type="text/css" media="all" href="style-ielt9.css"/> <![endif]−->
Technically it's one more alternative: using CSS hacks to target IE<9. It has the same impact as an IE<9 only stylesheet, but you don't need a separate stylesheet for that. I do not recommend this option, though, as they produce invalid CSS code (which is but one of several reasons why the use of CSS hacks is generally frowned upon today).
The most basic use of a float is having text wrap around an image. The below code will produce two paragraphs and an image, with the second paragraph flowing around the image. Notice that it is always content after the floated element that flows around the floated element.
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Integer nec odio. Praesent libero. Sed cursus ante dapibus diam. Sed
nisi. Nulla quis sem at nibh elementum imperdiet. Duis sagittis ipsum.
Praesent mauris. Fusce nec tellus sed augue semper porta. Mauris
massa. Vestibulum lacinia arcu eget nulla. </p>
<img src="http://lorempixel.com/200/100/" />
<p>Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.
Curabitur sodales ligula in libero. Sed dignissim lacinia nunc. Curabitur tortor. Pellentesque
nibh. Aenean quam. In scelerisque sem at dolor. Maecenas mattis. Sed convallis tristique sem. Proin
ut ligula vel nunc egestas porttitor. Morbi lectus risus, iaculis vel, suscipit quis, luctus non,
massa. Fusce ac turpis quis ligula lacinia aliquet. </p>
img {
float: left;
margin-right: 1rem;
}
The clear property is directly related to floats.
| Property Value | Description |
|---|---|
| none | Default. Allows floating elements on both sides. |
| left | No floating elements allowed on the left side. |
| right | No floating elements allowed on the right side. |
| both | No floating elements allowed on either the left or the right side. |
| initial | Sets this property to its default value. Read about initial. |
| inherit | Inherits this property from its parent element. Read about inherit. |
<html>
<head>
<style>
img {
float: left;
}
p.clear {
clear: both;
}
</style>
</head>
<body>
<img src="https://static.pexels.com/photos/69372/pexels-photo-69372-medium.jpeg" width="100">
<p>Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem
ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum </p>
<pclass="clear">Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum
Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum </p>
</body>
</html>
The clearfix hack is a popular way to contain floats (N. Gallagher aka @necolas)
Not to be confused with the clear property, clearfix is a concept (that is also related to floats, thus the possible confusion). To contain floats, you've to add .cf or .clearfix class on the container (the parent) and style this class with a few rules described below.
3 versions with slightly different effects (sources: A new micro clearfix hack by N. Gallagher and clearfix reloaded by T.J. Koblentx);
.cf: after {
content: "";
display: table;
}
.cf: after {
clear: both;
}
/**
* For modern browsers
* 1. The space content is one way to avoid an Opera bug when the
* contenteditable attribute is included anywhere else in the document.
* Otherwise it causes space to appear at the top and bottom of elements
* that are clearfixed.
* 2. The use of 'table' rather than 'block' is only necessary if using
* ':before' to contain the top-margins of child elements.
**/
.cf:before,
.cf:after {
content: " "; /* 1 */
display: table; /* 2 */
}
# .cf:after {
clear: both;
}
.cf:before,
.cf:after {
content: " ";
display: table;
}
.cf:after {
clear: both;
}
/**
* For IE 6/7 only
* Include this rule to trigger hasLayout and contain floats.
**/
.cf {
*zoom: 1;
}
Codepen showing ClearFix effect
Other resource: Everything you know about clearfix is wrong (clearfix and BFC - Block Formatting Context while has Layout relates to outdated browsers IE6 maybe 7)
The div is a block-level element, i.e it occupies the whole of the page width and the siblings are place one below the other irrespective of their width.
<div> <p>This is DIV 1</p> </div> <div> <p>This is DIV 2</p> </div>
The output of the following code will be;
We can make them in-line by adding a float css property to the div.
<div class="outer-div">
<div class="inner-div1">
<p>This is DIV 1</p>
</div>
<div class="inner-div2">
<p>This is DIV 2</p>
</div>
</div>
.inner-div1 {
width: 50%;
margin-right: 0px;
float: left;
background: #337ab7;
padding: 50px 0px;
}
.inner-div2 {
width: 50%;
margin-right: 0px;
float: left;
background: #dd2c00;
padding: 50px 0px;
}
p {
text-align: center;
}
Setting overflow value to hidden,auto or scroll to an element, will clear all the floats within that element.
Note: using overflow:scroll will always show the scrollbox.
A simple two-column layout consists of two fixed-width, floated elements. Note that the sidebar and content area are not the same height in this example. This is one of the tricky parts with multi-column layouts using floats, and requires workarounds to make multiple columns appear to be the same height.
<div class="wrapper">
<div class="sidebar">
<h2>Sidebar</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer nec odio.</p>
</div>
<div class="content">
<h1>Content</h1>
<p>Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.
Curabitur sodales ligula in libero. Sed dignissim lacinia nunc. Curabitur tortor. Pellentesque
nibh. Aenean quam. In scelerisque sem at dolor. Maecenas mattis. Sed convallis tristique sem. Proin
ut ligula vel nunc egestas porttitor. Morbi lectus risus, iaculis vel, suscipit quis, luctus non,
massa. Fusce ac turpis quis ligula lacinia aliquet. </p>
</div>
</div>
.wrapper {
width: 600px;
padding: 20px;
background-color: pink;
/* Floated elements don't use any height. Adding "overflow:hidden;"
forces the parent element to expand to contain its floated children. */
overflow: hidden;
}
.sidebar {
width: 150px;
float: left;
background-color: blue;
}
.content {
width: 450px;
float: right;
background-color: yellow;
}
<div class="wrapper">
<div class="left-sidebar">
<h1>Left Sidebar</h1>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. </p>
</div>
<div class="content">
<h1>Content</h1>
<p>Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.
Curabitur sodales ligula in libero. Sed dignissim lacinia nunc. Curabitur tortor. Pellentesque
nibh. Aenean quam. In scelerisque sem at dolor. Maecenas mattis. Sed convallis tristique sem. Proin
ut ligula vel nunc egestas porttitor. Morbi lectus risus, iaculis vel, suscipit quis, luctus non,
massa. </p>
</div>
<div class="right-sidebar">
<h1>Right Sidebar</h1
<p>Fusce ac turpis quis ligula lacinia aliquet.</p>
</div>
</div>
.wrapper {
width: 600px;
background-color: pink;
padding: 20px;
/* Floated elements don't use any height. Adding "overflow:hidden;"
forces the parent element to expand to contain its floated children. */
overflow: hidden;
}
.left-sidebar {
width: 150px;
background-color: blue;
float: left;
}
.content {
width: 300px;
background-color: yellow;
float: left;
}
.right-sidebar {
width: 150px;
background-color: green;
float: right;
}
This layout uses one floated column to create a two-column layout with no defined widths. In this example the left sidebar is "lazy," in that it only takes up as much space as it needs. Another way to say this is that the left sidebar is "shrink-wrapped." The right content column is "greedy," in that it takes up all the remaining space.
<div class="sidebar">
<h1>Sidebar</h1>
<img src="http://lorempixel.com/150/200/" />
</div>
<div class="content">
<h1>Content</h1>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer nec odio. Praesent libero. Sed
cursus ante dapibus diam. Sed nisi. Nulla quis sem at nibh elementum imperdiet. Duis sagittis
ipsum. Praesent mauris. Fusce nec tellus sed augue semper porta. Mauris massa. Vestibulum lacinia
arcu eget nulla. </p>
<p>Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.
Curabitur sodales ligula in libero. Sed dignissim lacinia nunc. Curabitur tortor. Pellentesque
nibh. Aenean quam. In scelerisque sem at dolor. Maecenas mattis. Sed convallis tristique sem. Proin
ut ligula vel nunc egestas porttitor. Morbi lectus risus, iaculis vel, suscipit quis, luctus non,
massa. Fusce ac turpis quis ligula lacinia aliquet. Mauris ipsum. Nulla metus metus, ullamcorper
vel, tincidunt sed, euismod in, nibh. </p>
</div>
.sidebar { /* 'display:table;' shrink-wraps the column */
display: table; float: left; background-color:
blue; } .content { /* 'overflow:hidden;' prevents '.content' from
flowing under '.sidebar' */
overflow: hidden;
background-color: yellow;
}
Demo (jsFiddle) class='sidebar'.
| Parameter | Details |
|---|---|
| font-style | italics or oblique |
| font-variant | normal or small-caps |
| font-weight | normal, bold or numeric from 100 to 900. |
| font-size | The font size given in %, px, em, or any other valid CSS measurement. |
| line-height | The line height given in %, px, em, or any other valid CSS measurement. |
| font-family | This is for defining the family's name. |
| color | Any valid CSS color representation, like red, #00FF00,hsl(240, 100%, 50%) etc. |
| font-stretch | Whether or not to use a confenced or expanded face from font. Valid values are normal, ultra- |
| condensed, extra-condensed, condensed, semi-condensed, semi-expanded, expanded, extra- | |
| expanded or ultra-expanded. | |
| text-align | start, end, left, right, center, justify, match-parent |
| text-decoration | none, underline, overline, line-through, initial, inherit; |
With the syntax:
element {
font: [font-style] [font-variant] [font-weight] [font-size/line-height] [font-family];
}
You can have all your font-related styles in one declaration with the font shorthand. Simply use the font property, and put your values in the correct order.
For example, to make all p elements bold with a font size of 20px and using Arial as the font family typically you would code it as follows:
p {
font-weight: bold;
font-size: 20px;
font-family: Arial, sans-serif;
}
However with the font shorthand it can be condensed as follows:
p {
font: bold 20px Arial, sans-serif;
}
Note: that since font-style, font-variant, font-weight and line-height are optional, the three of them are skipped in this example. It is important to note that using the shortcut resets the other attributes not given. Another important point is that the two necessary attributes for the font shortcut to work are font-size and fontfamily. If they are not both included the shortcut is ignored.
Initial value for each of the properties:
<div id="element-one">Hello I am some text.</div> <div id="element-two">Hello I am some smaller text.</div>
#element-one {
font-size: 30px;
}
#element-two {
font-size: 10px;
}
The text inside #element-one will be 30px in size, while the text in #element-two will be 10px in size.
div {
direction: ltr; /* Default, text read read from left-to-right */
}
.ex {
direction: rtl; /* text read from right-to-left */
}
.horizontal-tb {
writing-mode: horizontal-tb; /* Default, text read from left-to-right and top-to-bottom. */
}
.vertical-rtl {
writing-mode: vertical-rl; /* text read from right-to-left and top-to-bottom */
}
.vertical-ltr {
writing-mode: vertical-rl; /* text read from left-to-right and top to bottom */
}
The direction property is used to change the horizontal text direction of an element.
The writing-mode property changes the alignment of text so it can be read from top-to-bottom or from left-to-right, depending on the language.
font-family: 'Segoe UI', Tahoma, sans-serif;
The browser will attempt to apply the font face "Segoe UI" to the characters within the elements targeted by the above property. If this font is not available, or the font does not contain a glyph for the required character, the browser will fall back to Tahoma, and, if necessary, any sans-serif font on the user's computer. Note that any font names with more than one word such as "Segoe UI" need to have single or double quotes around them.
font-family: Consolas, 'Courier New', monospace;
The browser will attempt to apply the font face "Consolas" to the characters within the elements targeted by the above property. If this font is not available, or the font does not contain a glyph for the required character, the browser will fall back to "Courier New," and, if necessary, any monospace font on the user's computer.
The text-overflow property deals with how overflowed content should be signaled to users. In this example, the ellipsis represents clipped text.
.text {
overflow: hidden;
text-overflow: ellipsis;
}
Unfortunately, this only works on a single line of text. There is no way to support ellipsis on the last line in standard CSS, but it can be achieved with non-standard webkit-only implementation of flexboxes.
.giveMeEllipsis {
overflow: hidden;
text-overflow: ellipsis;
display: -webkit-box;
-webkit-box-orient: vertical;
-webkit-line-clamp: N; /* number of lines to show */
line-height: X; /* fallback */
max-height: X*N; /* fallback */
}
Example (open in Chrome or Safari):
Demo (jsFiddle) Text Overflow.
To add shadows to text, use the text-shadow property. The syntax is as follows:
text-shadow: horizontal-offset vertical-offset blur color;
This creates a blue shadow effect around a heading.
This creates a blue shadow effect around a heading.
To add a blur effect, add an option blur radius argument.
h1 {
text-shadow: 2px 2px 10px #0000FF;
}
To give an element multiple shadows, separate them with commas.
h1 {
text-shadow: 0 0 3px #FF0000, 0 0 5px #0000FF;
}
The text-transform property allows you to change the capitalization of text. Valid values are: uppercase, capitalize, lowercase, initial, inherit, and none.
.example1 {
text-transform: uppercase;
}
.example2 {
text-transform: capitalize;
}
.example3 {
text-transform: lowercase;
}
<p class="example1"> all letters in uppercase<!−-"ALL LETTERS IN UPPERCASE"−-> </p> <pclass ="example2"> all letters in capitalize<!−-"All Letters In Capitalize (Sentence Case)"−-> </p> <p class="example3"> all letters in lowercase<!−-"all letters in lowercase"−-> </p>
h2 {
/* adds a 1px space horizontally between each letter;
also known as tracking */
letter-spacing: 1px;
}
The letter-spacing property is used to specify the space between the characters in a text.
!letter-spacing also supports negative values:
p {
letter-spacing: -1px;
}
Resources: Letter Spacing
p {
text-indent: 50px;
}
The text-indent property specifies how much horizontal space text should be moved before the beginning of the first line of the text content of an element.
The text-decoration property is used to set or remove decorations from text.
h1 { text-decoration: none; }
h2 { text-decoration: overline; }
h3 { text-decoration: line-through; }
h4 { text-decoration: underline; }
text-decoration can be used in combination with text-decoration-style and text-decoration-color as a shorthand property:
.title { text-decoration: underline dotted blue; }
This is a shorthand version of
.title
{
text-decoration-style: dotted;
text-decoration-line: underline;
text-decoration-color: blue;
}
It should be noted that the following properties are only supported in Firefox
The word-spacing property specifies the spacing behavior between tags and words.
.normal { word-spacing: normal; }
.narrow { word-spacing: -3px; }
.extensive {word-spacing: 10px; }
<p> <span class="normal">This is an example, showing the effect of "word-spacing".</span><br> <span class="narrow">This is an example, showing the effect of "word-spacing".</span><br> <span class="extensive">This is an example, showing the effect of "word-spacing".</span><br> </p>
Default attribute of fonts.
Sets every letter to uppercase, but makes the lowercase letters(from original text) smaller in size than the letters that originally uppercase.
.smallcaps {
font-variant: small-caps;
}
<p class="smallcaps"> Documentation about CSS Fonts <br> aNd ExAmpLe </p>
Note: The font-variant property is a shorthand for the properties: font-variant-caps, font-variant-numeric, fontvariant-alternates, font-variant-ligatures, and font-variant-east-asian.
The Flexible Box module, or just 'flexbox' for short, is a box model designed for user interfaces, and it allows users to align and distribute space among items in a container such that elements behave predictably when the page layout must accommodate different, unknown screen sizes. A flex container expands items to fill available space and shrinks them to prevent overflow.
<div class="aligner"> <div class="aligner-item">...</div> </div>
.aligner {
display: flex;
align-items: center;
justify-content: center;
}
.aligner-item {
max-width: 50%; /* for demo. Use actual width instead. */
}
Here is a demo (CodePen).
| Property | Value | Description |
|---|---|---|
| align-items | center | This centers the elements along the axis other than the one specified by flex-direction, |
| i.e., vertical centering for a horizontal flexbox and horizontal centering for a vertical | ||
| flexbox. | ||
| justify-content | center | This centers the elements along the axis specified by flex-direction. I.e., for a |
| horizontal (flex-direction: row) flexbox, this centers horizontally, and for a vertical | ||
| flexbox (flex-direction: column) flexbox, this centers vertically. |
All of the below styles are applied onto this simple layout:
<div id="container"> <div></div> <div></div> <div></div> </div>
where #container is the flex-box.
div#container {
display: flex;
flex-direction: row;
justify-content: center;
}
Here is the demo (jsFiddle).
div#container {
display: flex;
flex-direction: column;
justify-content: center;
}
Here is a demo (jsFiddle).
div#container {
display: flex;
flex-direction: row;
align-items: center;
}
Here is a demo jsFiddle.
div#container {
display: flex;
flex-direction: column;
align-items: center;
}
Here is a demo (jsFiddle).
div #container {
display: flex;
flex-direction: row;
justify-content: center;
align-items: center;
}
Here is a Demo (jsFiddle).
div #container {
display: flex;
flex-direction: column;
justify-content: center;
align-items: center;
}
Here is a demo (jsFiddle).
This code creates a sticky footer. When the content doesn't reach the end of the viewport, the footer sticks to the bottom of the viewport. When the content extends past the bottom of the viewport, the footer is also pushed out of the viewport.
<div class="header"> <h2>Header</h2> </div> <div class="content"> <h1>Content</1> <p> Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer nec odio. Praesent libero. Sed cursus ante dapibus diam. Sed nisi. Nulla quis sem at nibh elementum imperdiet. Duis sagittis ipsum. Praesent mauris. Fusce nec tellus sed augue semper porta. Mauris massa. Vestibulum lacinia arcu eget nulla. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Curabitur sodales ligula in libero. </p> </div> <div class="footer"> <h4>Footer</h4> </div>CSS:
html, body {
height: 100%;
}
body {
display: flex;
flex-direction: column;
}
.content {
/* Include '0 auto' for best browser compatibility. */
flex: 10 auto;
}
.header, .footer {
background-color: grey;
color: white;
flex: none;
}
One of the nicest features of flexbox is to allow optimally fitting containers to their parent element.
<div class = "flex-container"> <div class = "flex-item">1 </div> <div class = "flex-item">2 </div> <div class = "flex-item">3 </div> <div class = "flex-item">4 </div> <div class = "flex-item">5 </div> </div>
.flex-container {
background-color:#000;
height:100%; display: flex; flex-direction: row;
flex-wrap: wrap; justify-content: flex-start; align-content: stretch;
align-items: stretch;
}
.flex-item {
background-color: #ccf;
margin:0.1em; flex-grow: 1;
flex-shrink:0;
flex-basis:200px; /* or % could be used to ensure a specific layout */
}
Columns adapt as screen is resized.
Holy Grail layout is a layout with a fixed height header and footer, and a center with 3 columns. The 3 columns include a fixed width sidenav, a fluid center, and a column for other content like ads (the fluid center appears first in the markup). CSS Flexbox can be used to achieve this with a very simple markup:
<div class="container">
<header class="header">Header</header>
<div class="content-body">
<main class="content">Content</main>
<nav class="sidenav">Nav</nav>
<aside class="ads">Ads</aside>
</div>
<footer class="footer">Footer</footer>
</div>
body {
margin: 0;
padding: 0;
}
.container {
display: flex;
flex-direction: column;
height: 100vh;
}
.header {
flex: 0 0 50px;
}
.content-body {
flex: 1 1 auto;
display: flex;
flex-direction: row;
}
.content-body
.content {
flex: 1 1 auto;
overflow: auto;
}
.content-body .sidenav {
order: − 1;
flex: 0 0 100px;
overflow: auto;
}
.content-body .ads {
flex: 0 0 100px;
overflow: auto;
}
.footer {
flex: 0 0 50px;
}
Demo (jsFiddle)
It's a regular pattern in design these days to vertically align call to actions inside its containing cards like this:
This can be achieved using a special trick with flexbox.
<div class="cards">
<div class="card">
<p>Lorem ipsum Magna proident ex anim dolor ullamco pariatur reprehenderit culpa esse enim
mollit labore dolore voluptate ullamco et ut sed qui minim.</p>
<p><button>Action</button></p>
</div>
<div class="card">
<p>Lorem ipsum Magna proident ex anim dolor ullamco pariatur reprehenderit culpa esse enim
mollit labore dolore voluptate ullamco et ut sed qui minim.</p>
<p>Lorem ipsum Magna proident ex anim dolor ullamco pariatur reprehenderit culpa esse enim
mollit labore dolore voluptate ullamco et ut sed qui minim.</p>
<p>Lorem ipsum Magna proident ex anim dolor ullamco pariatur reprehenderit culpa esse enim
mollit labore dolore voluptate ullamco et ut sed qui minim.</p>
<p>Lorem ipsum Magna proident ex anim dolor ullamco pariatur reprehenderit culpa esse enim
mollit labore dolore voluptate ullamco et ut sed qui minim.</p>
<p><button>Action</button></p>
</div>
</div>
First of all, we use CSS to apply display: flex; to the container. This will create 2 columns equal in height with the content flowing naturally inside it.
.cards {
display: flex;
}
.card {
border: 1px solid #ccc;
margin: 10px 10px;
padding: 0 20px;
}
button {
height: 40px;
background: #fff;
padding: 0 40px;
border: 1px solid #000;
}
p: last-child {
text-align: center;
}
In order to move the buttons to the bottom of the block, we need to apply display: flex; to the card itself with the direction set to column. After that, we should select the last element inside the card and set the margin-top to auto. This will push the last paragraph to the bottom of the card and achieve the required result.
.cards {
display: flex;
}
.card {
border: 1px solid #ccc;
margin: 10px 10px;
padding: 0 20px;
display: flex;
flex-direction: column; }
button {
height: 40px;
background: #fff;
padding: 0 40px;
border: 1px solid #000;
}
p: last-child {
text-align: center;
margin-top: auto;
}
This code makes sure that all nested containers are always the same height. This is done by assuring that all nested elements are the same height as the containing parent div. See working example:
This effect is achieved due to the property align-items being set to stretch by default.
<div class="container">
<div style="background-color: red">
Some <br/>
data <br />
to make <br />
a height <br />
</div>
<div style="background-color: blue">
Fewer <br />
lines <br />
</div>
</div>
.container {
display: flex;
align-items: stretch; // Default value
}
Note: Does not work on IE versions under 10.
Each individual CSS Selector has its own specificity value. Every selector in a sequence increases the sequence's overall specificity. Selectors fall into one of three different specificity groups: A, B and c. When multiple selector sequences select a given element, the browser uses the styles applied by the sequence with the highest overall specificity.
| Group | Comprised of | Examples |
|---|---|---|
| A | id selectors | #foo |
| B | class selectors | .bar |
| attribute selectors | [title], [colspan="2"] | |
| pseudo-classes | :hover, :nth-child(2) | |
| C | type selectors | div, li |
| pseudo-elements | ::before, ::first-letter |
Group A is the most specific, followed by Group B, then finally Group C.
The universal selector (*) and combinators (like > and ~) have no specificity.
#foo #baz {} /* a=2, b=0, c=0 */
#foo .bar {} /* a=1, b=1, c=0 */
#foo {} /* a=1, b=0, c=0 */
.bar: hover {} /* a=0, b=2, c=0 */
div.bar {} /* a=0, b=1, c=1 */
:hover {} /* a=0, b=1, c=0 */
[title] {} /* a=0, b=1, c=0 */
.bar {} /* a=0, b=1, c=0 */
div ul + li {} /* a=0, b=0, c=3 */
p::after {} /* a=0, b=0, c=2 */
*::before {} /* a=0, b=0, c=1 */
::before {} /* a=0, b=0, c=1 */
div {} /* a=0, b=0, c=1 */
* {} /* a=0, b=0, c=0 */
Imagine the following CSS implementation:
#foo {
color: blue;
}
.bar {
color: red;
background: black;
}
Here we have an ID selector which declares color as blue, and a class selector which declares color as red and background as black.
An element with an ID of #foo and a class of .bar will be selected by both declarations. ID selectors have a Group A specificity and class selectors have a Group B specificity. An ID selector outweighs any number of class selectors. Because of this, color: blue; from the #foo selector will be applied to the element. The higher specificity of the ID selector will cause the browser to ignore the .bar selector's color declaration.
.bar {
color: red;
background: black;
}
.baz {
background: white;
}
Here we have two class selectors; one of which declares color as red and background as black, and the other declares background as white.
An element with both the .bar and .baz classes will be affected by both of these declarations, however the problem we have now is that both .bar and .baz have an identical Group B specificity. The cascading nature of CSS resolves this for us: as .baz is defined after .bar, our element ends up with the red color from .bar but the white background from .baz.
The last snippet from Example 2 above can be manipulated to ensure our .bar class selector's color declaration is used instead of that of the .baz class selector.
.bar {} /* a=0, b=1, c=0 */
.baz {} /* a=0, b=1, c=0 */
The most common way to achieve this would be to find out what other selectors can be applied to the .bar selector sequence. For example, if the .bar class was only ever applied to span elements, we could modify the .bar selector to span.bar. This would give it a new Group C specificity, which would override the .baz selector's lack thereof:
span .bar {} /* a=0, b=1, c=1 */
.baz {} /* a=0, b=1, c=0 */
However it may not always possible to find another common selector which is shared between any element which uses the .bar class. Because of this, CSS allows us to duplicate selectors to increase specificity. Instead of just .bar, we can use instead (See The grammar of Selectors, W3C Recommendation). This still selects any element with a class of .bar, but now has double the Group B specificity:
.bar.bar {} /* a=0, b=2, c=0 */
.baz {} /* a=0, b=1, c=0 */
The !important flag on a style declaration and styles declared by the HTML style attribute are considered to have a greater specificity than any selector. If these exist, the style declaration they affect will overrule other declarations regardless of their specificity. That is, unless you have more than one declaration that contains an !important flag for the same property that apply to the same element. Then, normal specificity rules will apply to those properties in reference to each other.
Because they completely override specificity, the use of !important is frowned upon in most use cases. One should use it as little as possible. To keep CSS code efficient and maintainable in the long run, it's almost always better to increase the specificity of the surrounding selector than to use !important.
One of those rare exceptions where !important is not frowned upon, is when implementing generic helper classes like a .hidden or .background-yellow class that are supposed to always override one or more properties wherever they are encountered. And even then, you need > to know what you're doing. The last thing you want, when writing maintainable CSS, is to have !important flags throughout your CSS.
A common misconception about CSS specificity is that the Group A, B and c values should be combined with each other (a=1,=1 => 151). This is not the case. If this were the case, having 20 of a Group B or c selector would be enough to override a single Group A or B selector respectively. The three groups should be regarded as individual levels of specificity. Specificity cannot be represented by a single value.
When creating your CSS style sheet, you should maintain the lowest specificity as possible. If you need to make the specificity a little higher to overwrite another method, make it higher but as low as possible to make it higher. You shouldn't need to have a selector like this:
body.page header.container nav div#main-nav li a {}
This makes future changes harder and pollutes that css page.
You can calculate the specificity of your selector here.
The !important declaration is used to override the usual specificity in a style sheet by giving a higher priority to a rule. Its usage is: property : value !important;
#mydiv {
font-weight: bold !important; /* This property won't be overridden
by the rule below */
}
#outerdiv #mydiv {
font-weight: normal; /* #mydiv font-weight won't be set to normal
even if it has a higher specificity because
of the !important declaration above */
}
Avoiding the usage of !important is strongly recommended (unless absolutely necessary), because it will disturb the natural flow of css rules which can bring uncertainty in your style sheet. Also it is important to note that when multiple !important declarations are applied to the same rule on a certain element, the one with the higher specificity will be the ona applied.
Here are some examples where using !important declaration can be justified:
W3C - 6 Assigning property values, Cascading, and Inheritance −-6.4.2 !important rules.
Cascading and specificity are used together to determine the final value of a CSS styling property. They also define the mechanisms for resolving conflicts in CSS rule sets.
Styles are read from the following sources, in this order:
The browser will lookup the corresponding style(s) when rendering an element.
When only one CSS rule set is trying to set a style for an element, then there is no conflict, and that rule set is used.
When multiple rule sets are found with conflicting settings, first the Specificty rules, and then the Cascading rules are used to determine what style to use.
.mystyle { color: blue; } /* specificity: 0, 0, 1, 0 */
div { color: red; } /* specificity: 0, 0, 0, 1 */
<div class="mystyle">Hello World</div>
What color will the text be? (hover to see the answer)
blue
First the specificity rules are applied, and the one with the highest specificity "wins".
.class {
background: #FFF;
}
<style>
.class {
background: #000;
}
<style>
In this case, where you have identical selectors, the cascade kicks in, and determines that the last one loaded "wins".
body > .mystyle { background-color: blue; } /* specificity: 0, 0, 1, 1 */
.otherstyle > div { background-color: red; } /* specificity: 0, 0, 1, 1 */
<body class="otherstyle">
<div class="mystyle">Hello World</div>
</body>
What color will the background be?
red
After applying the specificity rules, there's still a conflict between blue and red, so the cascading rules are applied on top of the specificity rules. Cascading looks at the load order of the rules, whether inside the same .css file or in the collection of style sources. The last one loaded overrides any earlier ones. In this case, the rule "wins".
div {
font-size: 7px;
border: 3px dotted pink;
background-color: yellow;
color: purple;
}
body.mystyle > div.myotherstyle {
font-size: 11px;
background-color: green;
}
#elmnt1 {
font-size: 24px;
border-color: red;
}
.mystyle .myotherstyle {
font-size: 16px;
background-color: black;
color: red;
}
<body class="mystyle">
<div id="elmnt1" class="myotherstyle">
Hello, world!
</div>
</body>
What borders, colors, and font-sizes will the text be? font-size:
font-size: 24; Since #elmnt1 rule set has the highest specificity <div in question, every property here is set.
border: 3px dotted red; The border color red is take from #elmnt1 rule set, since it has the highest specificity. The other properties of the border, border-thickness, and border-style are from the div rule set.
background-color: green; The background-color is set in the div, body.mystyle > div.myotherstyle and .mystyle .myotherstyle rule sets. The specificities are (0,0,1)vs.(0,2,2)vs.(0,2,0), so the middle one “wins”.
color: red; The color is set in both the div and .mystyle .myotherstyle rule sets. The latter has the higher specificity of (0,2,0) and “wins”.
currentColor returns the computed color value of the current element.
Here currentColor evaluates to red since the color property is set to red:
div {
color: red;
border: 5px solid currentColor;
box-shadow: 0 0 5px currentColor;
}
In this case, specifying currentColor for the border is most likely redundant because omitting it should produce identical results. Only use currentColor inside the border property within the same element if it would be overwritten otherwise due to a more specific selector.
Since it's the computed color, the border will be green in the following example due to the second rule overriding the first:
div {
color: blue;
border: 3px solid currentColor;
color: green;
}
The parent's color is inherited, here currentColor evaluates to 'blue', making the child element's border-color blue.
.parent-class {
color: blue;
}
.parent-class .child-class {
border-color: currentColor;
}
currentColor can also be used by other rules which normally would not inherit from the color property, such as background-color. The example below shows the children using the color set in the parent as its background:
.parent-class {
color: blue;
}
.parent-class .child-class {
background-color: currentColor;
}
Most browsers support using color keywords to specify a color. For example, to set the color of an element to blue, use the blue keyword:
.some-class {
color: blue;
}
CSS keywords are not case sensitive—blue, Blue and BLUE will all result in #0000FF.
| Color name | Hex value | RGB values |
|---|---|---|
| AliceBlue - Very pale (mostly white) blue. | #F0F8FF | rgb(240,248,255) |
| AntiqueWhite - Grayish orange | #FAEBD7 | rgb(250,235,215) |
| Aqua - Pure (or mostly pure) cyan | #00FFFF | rgb(0,255,255) |
| Aquamarine - Very light cyan - lime green | #7FFFD4 | rgb(127,255,212) |
| Azure - Very pale (mostly white) cyan | #F0FFFF | rgb(240,255,255) |
| Beige - Light grayish yellow | #F5F5DC | rgb(245,245,220) |
| Bisque - Very pale orange | #FFE4C4 | rgb(255,228,196) |
| Black | #000000 | rgb(0,0,0) |
| BlanchedAlmond - Very pale orange | #FFEBCD | rgb(255,235,205) |
| Blue - Pure (or mostly pure) blue | #0000FF | rgb(0,0,255) |
| BlueViolet - Bright violet | #8A2BE2 | rgb(138,43,226) |
| Brown - Dark red | #A52A2A | rgb(165,42,42) |
| BurlyWood - Very soft orange | #DEB887 | rgb(222,184,135) |
| CadetBlue - Mostly desaturated dark cyan | #5F9EA0 | rgb(95,158,160) |
| Chartreuse - Pure (or mostly pure) green | #7FFF00 | rgb(127,255,0) |
| Chocolate - Strong orange | #D2691E | rgb(210,105,30) |
| Coral - Light orange | #FF7F50 | rgb(255,127,80) |
| CornflowerBlue - Soft blue | #6495ED | rgb(100,149,237) |
| Cornsilk - Very pale yellow | #FFF8DC | rgb(255,248,220) |
| Crimson | #DC143C | rgb(220,20,60) |
| Cyan | #00FFFF | rgb(0,255,255) |
| DarkBlue | #00008B | rgb(0,0,139) |
| DarkCyan | #008B8B | rgb(0,139,139) |
| DarkGoldenRod | #B8860B | rgb(184,134,11) |
| DarkGray | #A9A9A9 | rgb(169,169,169) |
| DarkGrey | #A9A9A9 | rgb(169,169,169) |
| DarkGreen | #006400 | rgb(0,100,0) |
| DarkKhaki | #BDB76B | rgb(189,183,107) |
| DarkMagenta | #8B008B | rgb(139,0,139) |
| DarkOliveGreen | #556B2F | rgb(85,107,47) |
| DarkOrange | #FF8C00 | rgb(255,140,0) |
| DarkOrchid | #9932CC | rgb(153,50,204) |
| DarkRed | #8B0000 | rgb(139,0,0) |
| DarkSalmon | #E9967A | rgb(233,150,122) |
| DarkSeaGreen | #8FBC8F | rgb(143,188,143) |
| DarkSlateBlue | #483D8B | rgb(72,61,139) |
| DarkSlateGray | #2F4F4F | rgb(47,79,79) |
| DarkSlateGrey | #2F4F4F | rgb(47,79,79) |
| DarkTurquoise | #00CED1 | rgb(0,206,209) |
| DarkViolet | #9400D3 | rgb(148,0,211) |
| DeepPink | #FF1493 | rgb(255,20,147) |
| DeepSkyBlue | #00BFFF | rgb(0,191,255) |
| DimGray | #696969 | rgb(105,105,105) |
| DimGrey | #696969 | rgb(105,105,105) |
| DodgerBlue | #1E90FF | rgb(30,144,255) |
| FireBrick | #B22222 | rgb(178,34,34) |
| FloralWhite | #FFFAF0 | rgb(255,250,240) |
| ForestGreen | #228B22 | rgb(34,139,34) |
| Fuchsia | #FF00FF | rgb(255,0,255) |
| Gainsboro | #DCDCDC | rgb(220,220,220) |
| GhostWhite | #F8F8FF | rgb(248,248,255) |
| Gold | #FFD700 | rgb(255,215,0) |
| GoldenRod | #DAA520 | rgb(218,165,32) |
| Gray | #808080 | rgb(128,128,128) |
| Grey | #808080 | rgb(128,128,128) |
| Green | #008000 | rgb(0,128,0) |
| GreenYellow | #ADFF2F | rgb(173,255,47) |
| HoneyDew | #F0FFF0 | rgb(240,255,240) |
| HotPink | #FF69B4 | rgb(255,105,180) |
| IndianRed | #CD5C5C | rgb(205,92,92) |
| Indigo - Dark violet | #4B0082 | rgb(75,0,130) |
| Ivory - Very pale yellow | #FFFFF0 | rgb(255,255,240) |
| Khaki - Very soft yellow | #F0E68C | rgb(240,230,140) |
| Lavender | #E6E6FA | rgb(230,230,250) |
| LavenderBlush | #FFF0F5 | rgb(255,240,245) |
| LawnGreen | #7CFC00 | rgb(124,252,0) |
| LemonChiffon | #FFFACD | rgb(255,250,205) |
| LightBlue | #ADD8E6 | rgb(173,216,230) |
| LightCoral | #F08080 | rgb(240,128,128) |
| LightCyan | #E0FFFF | rgb(224,255,255) |
| LightGoldenRodYellow | #FAFAD2 | rgb(250,250,210) |
| LightGray | #D3D3D3 | rgb(211,211,211) |
| LightGrey | #D3D3D3 | rgb(211,211,211) |
| LightGreen | #90EE90 | rgb(144,238,144) |
| LightPink | #FFB6C1 | rgb(255,182,193) |
| LightSalmon | #FFA07A | rgb(255,160,122) |
| LightSeaGreen | #20B2AA | rgb(32,178,170) |
| LightSkyBlue | #87CEFA | rgb(135,206,250) |
| LightSlateGray | #778899 | rgb(119,136,153) |
| LightSlateGrey | #778899 | rgb(119,136,153) |
| LightSteelBlue | #B0C4DE | rgb(176,196,222) |
| LightYellow | #FFFFE0 | rgb(255,255,224) |
| Lime | #00FF00 | rgb(0,255,0) |
| LimeGreen | #32CD32 | rgb(50,205,50) |
| Linen | #FAF0E6 | rgb(250,240,230) |
| Magenta | #FF00FF | rgb(255,0,255) |
| Maroon | #800000 | rgb(128,0,0) |
| MediumAquaMarine | #66CDAA | rgb(102,205,170) |
| MediumBlue | #0000CD | rgb(0,0,205) |
| MediumOrchid | #BA55D3 | rgb(186,85,211) |
| MediumPurple | #9370DB | rgb(147,112,219) |
| MediumSeaGreen | #3CB371 | rgb(60,179,113) |
| MediumSlateBlue | #7B68EE | rgb(123,104,238) |
| MediumSpringGreen | #00FA9A | rgb(0,250,154) |
| MediumTurquoise | #48D1CC | rgb(72,209,204) |
| MediumVioletRed | #C71585 | rgb(199,21,133) |
| MidnightBlue | #191970 | rgb(25,25,112) |
| MintCream | #F5FFFA | rgb(245,255,250) |
| MistyRose | #FFE4E1 | rgb(255,228,225) |
| Moccasin | #FFE4B5 | rgb(255,228,181) |
| NavajoWhite | #FFDEAD | rgb(255,222,173) |
| Navy | #000080 | rgb(0,0,128) |
| OldLace | #FDF5E6 | rgb(253,245,230) |
| Olive | #808000 | rgb(128,128,0) |
| OliveDrab | #6B8E23 | rgb(107,142,35) |
| Orange | #FFA500 | rgb(255,165,0) |
| OrangeRed | #FF4500 | rgb(255,69,0) |
| Orchid | #DA70D6 | rgb(218,112,214) |
| PaleGoldenRod | #EEE8AA | rgb(238,232,170) |
| PaleGreen | #98FB98 | rgb(152,251,152) |
| PaleTurquoise | #AFEEEE | rgb(175,238,238) |
| PaleVioletRed | #DB7093 | rgb(219,112,147) |
| PapayaWhip | #FFEFD5 | rgb(255,239,213) |
| PeachPuff | #FFDAB9 | rgb(255,218,185) |
| Peru | #CD853F | rgb(205,133,63) |
| Pink | #FFC0CB | rgb(255,192,203) |
| Plum | #DDA0DD | rgb(221,160,221) |
| PowderBlue | #B0E0E6 | rgb(176,224,230) |
| Purple | #800080 | rgb(128,0,128) |
| RebeccaPurple | #663399 | rgb(102,51,153) |
| Red | #FF0000 | rgb(255,0,0) |
| RosyBrown | #BC8F8F | rgb(188,143,143) |
| RoyalBlue | #4169E1 | rgb(65,105,225) |
| SaddleBrown | #8B4513 | rgb(139,69,19) |
| Salmon | #FA8072 | rgb(250,128,114) |
| SandyBrown | #F4A460 | rgb(244,164,96) |
| SeaGreen | #2E8B57 | rgb(46,139,87) |
| SeaShell | #FFF5EE | rgb(255,245,238) |
| Sienna | #A0522D | rgb(160,82,45) |
| Silver - Light gray | #C0C0C0 | rgb(192,192,192) |
| SkyBlue - Very soft blue | #87CEEB | rgb(135,206,235) |
| SlateBlue - Moderate blue | #6A5ACD | rgb(106,90,205) |
| SlateGray - Dark grayish blue | #708090 | rgb(112,128,144) |
| SlateGrey - Dark grayish blue | #708090 | rgb(112,128,144) |
| Snow - Very pale (mostly white) red | #FFFAFA | rgb(255,250,250) |
| SpringGreen - Pure (or mostly pure) cyan - lime green | #00FF7F | rgb(0,255,127) |
| SteelBlue | #4682B4 | rgb(70,130,180) |
| Tan | #D2B48C | rgb(210,180,140) |
| Teal | #008080 | rgb(0,128,128) |
| Thistle | #D8BFD8 | rgb(216,191,216) |
| Tomato | #FF6347 | rgb(255,99,71) |
| Turquoise | #40E0D0 | rgb(64,224,208) |
| Violet | #EE82EE | rgb(238,130,238) |
| Wheat | #F5DEB3 | rgb(245,222,179) |
| White | #FFFFFF | rgb(255,255,255) |
| WhiteSmoke | #F5F5F5 | rgb(245,245,245) |
| Yellow | #FFFF00 | rgb(255,255,0) |
| YellowGreen - Strong green | #9ACD32 | rgb(154,205,50) |
In addition to the named colors, there is also the keyword transparent, which represents a fully-transparent black: rgba(0,0,0,0).
CSS colors may also be represented as a hex triplet, where the members represent the red, green and blue components of a color. Each of these values represents a number in the range of 00 to FF, or 0 to 255 in decimal notation. Uppercase and/or lowercase Hexadecimal values may be used (i.e. #3fc = #3FC = #33ffCC). The browser interprets #369 as #336699. If that is not what you intended but rather wanted #306090, you need to specify that explicitly.
The total number of colors that can be represented with hex notation is 256 ^ 3 or 16,777,216.
color: #rrggbb; color: #rgb;
| Value | Description |
|---|---|
| rr | 00-FF for the amount of red. |
| gg | 00-FF for the amount of green. |
| bb | 00-FF for the amount of blue. |
.some-class {
/* This is equivalent to using the color keyword 'blue' */
color: #0000FF;
}
.also-blue {
/* If you want to specify each range value with a single number, you can!
This is equivalent to '#0000FF' (and 'blue') */
color: #00F;
}
Hexadecimal notation is used to specify color values in the RGB color format, per the W3C's 'Numerical color values'.
There are a lot of tools available on the Internet for looking up hexadecimal (or simply hex) color values.
Search for "hex color palette" or "hex color picker" with your favorite web browser to find a bunch of options!
Hex values always start with a pound sign (#), are up to six "digits" long, and are case-insensitive: that is, they don't care about capitalization. #FFC125 and #ffc125 are the same color.
RGB is an additive color model which represents colors as mixtures of red, green, and blue light. In essence, the RGB representation is the decimal equivalent of the Hexadecimal Notation. In Hexadecimal each number ranges from 00-FF which is equivalent to 0-255 in decimal and 0%-100% in percentages.
.some-class {
/* Scalar RGB, equivalent to 'blue' */
color: rgb (0,0,255);
}
.also-blue {
/* Percentile RGB values */
color: rgb(0%, 0%, 100%);
}
rgb(<red>, <green>, <blue>)
| Value | Description |
|---|---|
| <red> | an integer from 0 - 255 or percentage from 0 - 100%. |
| <green> | an integer from 0 - 255 or percentage from 0 - 100%. |
| <blue> | an integer from 0 - 255 or percentage from 0 - 100%. |
Similar to rgb() notation, but with an additional alpha (opacity) value.
.red {
/* Opaque red */
color: rgba (255, 0, 0, 1);
}
.red-50p {
/* Half-translucent red. */
color: rgba(255, 0, 0, .5);
}
rgba(<red>, <green>, <blue>, <alpha>);
| Value | Description |
|---|---|
| <red> | an integer from 0 - 255 or percentage from 0 - 100%. |
| <green> | an integer from 0 - 255 or percentage from 0 - 100%. |
| <blue> | an integer from 0 - 255 or percentage from 0 - 100%. |
| <alpha> | a number from 0 - 1, where 0.0 is fully transparent and 1.0 is fully opaque. |
HSL stands for hue ("which color"), saturation ("how much color") and lightness ("how much white").
Hue is represented as an angle from 0° to 360° (without units), while saturation and lightness are represented as percentages.
p {
color: hsl(240, 100%, 50%); /* Blue */
}
color: hsl(<hue>, <saturation>%, <lightness>%);
| Value | Description |
|---|---|
| <hue> | specified in degrees around the color wheel (without units), where 0° is red, 60° is yellow, 120° is |
| green, 180° is cyan, 240° is blue, 300° is magenta, and 360° is red. | |
| <saturation> | specified in percentage where 0% is fully desaturated (grayscale) and 100% is fully saturated (vividly |
| colored). | |
| <lightness> | specified in percentage where 0% is fully blakc and 100% is fully white. |
Similar to hsl() notation, but with an added alpha (opacity) value.
hsla(240, 100%, 50%, 0) /* transparent */ hsla(240, 100%, 50%, 0.5) /* half-translucent blue */ hsla(240, 100%, 50%, 1) /* fully opaque blue */
hsla(<hue>, <saturation>%, <lightness>%, <alpha>);
| Value | Description |
|---|---|
| <hue> | specified in degrees around the color wheel (without units), where 0° is red, 60° is yellow, 120° is green, 180° is cyan, 240° is blue, 300° is magenta, and 360° is red. |
| <saturation> | percentage where 0% is fully desaturated (grayscale) and 100% is fully saturated (vividly colored). |
| <lightness> | percentage where 0% is fully black and 100% is fully white. |
| <alpha> | a number from 0 - 1 where 0 is fully transparent and 1 is fully opaque. |
An element's opacity can be set using the opacity property. Values can be anywhere from 0.0 (transparent) to 1.0 (opaque).
<div style="opacity:0.8;"> This is a partially transparent element </div>
| Property Value | Transparency |
|---|---|
| opacity: 1.0; | Opaque. |
| opacity: 0.75; | 25% transparent (75% Opaque). |
| opacity: 0.5; | 50% transparent (50% Opaque) |
| opacity: 0.25; | 75% transparent (25% Opaque) |
| opacity: 0.0; | Transparent |
To use opacity in all versions of IE, the order is:
.transparent-element {
/* for IE 8 & 9 */
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=60)"; // IE8
/* works in IE 8 & 9 too, but also 5, 6, 7 */
filter: alpha(opacity=60); // IE 5−7
/* Modern Browsers */
opacity: 0.6;
}
| Unit | Description |
|---|---|
| % | Define sizes in terms of parent objects or current object dependent on property |
| em | Relative to the font-size of the element (2em means 2 times the size of the current font) |
| rem | Relative to font-size of the root element |
| vw | Relative to 1% of the width of the viewport* |
| vh | Relative to 1% of the height of the viewport* |
| vmin | Relative to 1% of > viewport's* smaller dimension |
| vmax | Relative to 1% of viewport's* larger dimension |
| cm | centimeters |
| mm | millimeters |
| in | inches (1in = 96px = 2.54cm) |
| px | pixels (1px = 1/96th of 1in) |
| pt | points (1pt = 1/72 of 1in) |
| pc | picas (1pc = 12 pt) |
| s | seconds (used for animations and transitions) |
| ms | milliseconds (used for animations and transitions) |
| ex | Relative to the x-height of the current font |
| ch | Based on the width of the zero (0) character |
| fr | fractional unit (used for CSS Grid Layout) |
A CSS distance measurement is a number immediately followed by a length unit (px, em, pc, in, …)
CSS supports a number of length measurements units. They are absolute or relative.
You can use rem defined by the font-size of your html tag to style elements by setting their font-size to a value of rem and use em inside the element to create elements that scale with your global font-size.
<input type="button" value="Button"> <input type="range"> <input type="text" value="Text">
html {
font-size: 16px;
}
input[type="button"] {
font-size: 1rem;
padding: 0.5em 2em;
}
input[type="range"] {
font-size: 1rem;
width: 10em;
}
input[type=text] {
font-size: 1rem;
padding: 0.5em;
}
CSS3 introduces a few new units, including the rem unit, which stands for "root em". Let's look at how rem works.
First, let's look at the differences between em and rem.
The main issue with using rem for font sizing is that the values are somewhat difficult to use. Here is an example of some common font sizes expressed in rem units, assuming that the base size is 16px:
html {
font-size: 16px;
}
h1 {
font-size: 2rem; /* 32px */
}
p {
font-size: 1rem; /* 16px */
}
li {
font-size: 1.5em; /* 24px */
}
In other words, 1 vmin is equal to the smaller of 1 vh and 1 vw
1 vmax is equal to the larger of 1 vh and 1 vw
Note: vmax is not supported in:
CSS3 introduced two units for representing size.
div {
width: 20vw;
height: 20vh;
}
Above, the size for the div takes up 20% of the width and height of the viewport.
One of the useful unit when creating a responsive application.
Its size depends on its parent container.
( Parent Container's width ) * ( Percentage(%) ) = Output
Parent has 100px width while the Child has 50%.
On the output, the Child's width will be half(50%) of the Parent's, which is 50px.
<div class="parent">
PARENT
<div class="child">
CHILD
</div>
</div>
<style>
*{
color: #CCC;
}
.parent {
background-color: blue;
width: 100px;
}
.child {
background-color: green;
width: 50%;
}
</style>
| pseudo-element | Description |
|---|---|
| ::after | Insert content after the content of an element. |
| ::before | Insert content before the content of an element. |
| ::first-letter | Selects the first letter of each element. |
| ::first-line | Selects the first line of each element. |
| ::selection | Matches the portion of an element that is selected by a user. |
| ::backdrop | Used to create a backdrop that hides the underlying document for an |
| element in the top layer's | |
| ::placeholder | Allows you to style the placeholder text of a form element |
| (Experimental) | |
| ::marker | For applying list-style attributes on a given element (Experimental) |
| ::spelling-error | Represents a text segment which the browser has flagged as incorrectly |
| spelled (Experimental) | |
| ::grammar-error | Represents a text segment which the browser has flagged as |
| grammatically incorrect (Experimental) |
Pseudo-elements, just like pseudo-classes, are added to a CSS selectors but instead of describing a special state, they allow you to scope and style certain parts of an html element.
For example, the ::first-letter pseudo-element targets only the first letter of a block element specified by the selector.
Pseudo-elements are added to selectors but instead of describing a special state, they allow you to style certain parts of a document.
The content attribute is required for pseudo-elements to render; however, the attribute can have an empty value (e.g.content: "").
div::after {
content: 'after';
color: red;
border: 1px solid red;
}
div {
color: black;
border: 1px solid black;
padding: 1px;
}
div::before {
content: 'before';
color: green;
border: 1px solid green;
}
Pseudo-elements are often used to change the look of lists (mostly for unordered lists, ul).
The first step is to remove the default list bullets:
ul {
list-style-type: none;
}
Then you add the custom styling. In this example, we will create gradient boxes for bullets.
li:before {
content: "";
display: inline-block;
margin-right: 10px;
height: 10px;
width: 10px;
background: linear-gradient (red, blue);
}
<ul> <li>Test I</li> <li>Test II</li> </ul>
| Parameter | Details |
|---|---|
| static | Default value. Elements render in order, as they appear in the document flow. |
| The top, right, bottom, left and z-index properties do not apply. | |
| relative | The element is positioned relative to its normal position, so left:20px adds |
| 20 pixels to the element's LEFT position. | |
| fixed | The element is positioned relative to the browser window. |
| absolute | The element is positioned relative to its first positioned (not static) ancestor element. |
| initial | Sets this property to its default value. |
| inherit | Inherits this property from its parent element. |
| sticky | Experimental feature. It behaves like position: static within its parent until a given offset threshold } |
| is reached, then it acts as position: fixed. | |
| unset | Combination of initial and inherit. More info here. |
To change the default stack order positioned elements (position property set to relative, absolute or fixed), use the z-index property.
The higher the z-index, the higher up in the stacking context (on the z-axis) it is placed.
In the example below, a z-index value of 3 puts green on top, a z-index of 2 puts red just under it, and a z-index of 1 puts blue under that.
<div id="div1"></div> <div id="div2"></div> <div id="div3"></div>
div {
position: absolute;
height: 200px;
width: 200px;
}
div #div1 {
z-index: 1;
left: 0px;
top: 0px;
background-color: blue;
}
div #div2 {
z-index: 3;
left: 100px;
top: 100px;
background-color: green;
}
div #div3 {
z-index: 2;
left: 50px;
top: 150px;
background-color: red;
}
See a working example at Demo (jsFiddle).
z-index: [ number ] | auto;
| Parameter | Details |
|---|---|
| number | An integer value. A higher number is higher on the z-index stack. 0 is the default value. Negative |
| values are allowed. | |
| auto | Gives the element the same stacking context as its parent. (Default) |
All elements are laid out in a 3D axis in CSS, including a depth axis, measured by the z-index property. z-index only works on positioned elements: (see: Why does z-index need a defined position to work?). The only value where it is ignored is the default value, static.
Read about the z-index property and Stacking Contexts in the CSS Specification on layered presentation and at the Mozilla Developer Network.
When absolute positioning is used the box of the desired element is taken out of the Normal Flow and it no longer affects the position of the other elements on the page. Offset properties:
specify the element should appear in relation to its next non-static containing element.
.abspos {
position: absolute;
top: 0px;
left: 500px;
}
This code will move the box containing element with attribute down 0px and right 500px relative to its containing element.
Defining position as fixed we can remove an element from the document flow and set its position relatively to the browser window. One obvious use is when we want something to be visible when we scroll to the bottom of a long page.
#stickyDiv {
position: fixed;
top: 10px;
left: 10px;
}
Relative positioning moves the element in relation to where it would have been in normal flow .Offset properties:
are used to indicate how far to move the element from where it would have been in normal flow.
.relpos {
position: relative;
top: 20px;
left: 30px;
}
This code will move the box containing element with attribute class="relpos" 20px down and 30px to the right from where it would have been in normal flow.
The default position of an element is static. To quote MDN:
This keyword lets the element use the normal behavior, that is it is laid out in its current position in the flow. The top, right, bottom, left and z-index properties do not apply.
.element {
position: static;
}
| Value | Effect |
|---|---|
| none | Hide the element and prevent it from occupying space. |
| block | Block element, occupy 100% of the available width, break after element. |
| inline | Inline element, occupy no width, no break after element. |
| inline-block | Taking special properties from both inline and block elements, no break, but can have width. |
| inline-flex | Displays an element as an inline-level flex container. |
| inline-table | The element is displayed as an inline-level table. |
| grid | Behaves like a block element and lays out its content according to the grid model. |
| flex | Behaves like a block element and lays out its content according to the flexbox model. |
| inherit | Inherit the value from the parent element. |
| initial | Reset the value to the default value taken from behaviors described in the HTML specifications or |
| from the browser/user default stylesheet. | |
| table | Behaves like the HTML table element. |
| table-cell | Let the element behave like a <td> element. |
| table-column | Let the element behave like a <col> element. |
| table-row | Let the element behave like a <tr> element. |
| list-item | Let the element behave like a <li> element. |
The display CSS property is fundamental for controlling the layout and flow of an HTML document. Most elements have a default display value of either block or inline (though some elements have other default values).
An inline element occupies only as much width as necessary. It stacks horizontally with other elements of the same type and may not contain other non-inline elements.
<span>This is some <b>bolded</b> text!</span>
As demonstrated above, two inline elements, >, are in-line (hence the name) and do not break the flow of the text.
A block element occupies the maximum available width of its' parent element. It starts with a new line and, in contrast to inline elements, it does not restrict the type of elements it may contain.
<div>Hello world!</div><div>This is an example!</div>
The div element is block-level by default, and as shown above, the two block elements are vertically stacked and, unlike the inline elements, the flow of the text breaks.
The inline-block value gives us the best of both worlds: it blends the element in with the flow of the text while allowing us to use padding, margin, height and similar properties which have no visible effect on inline elements.
Elements with this display value act as if they were regular text and as a result are affected by rules controlling the flow of text such as text-align. By default they are also shrunk to the the smallest size possible to accommodate their content.
<!−-Inline: unordered list−->
<style>
li {
display : inline;
background : lightblue;
padding:10px;
border-width:2px;
border-color:black;
border-style:solid;
}
</style>
<ul>
<li>First Element </li>
<li>Second Element </li>
<li>Third Element </li>
</ul>
<!−-block: unordered list−->
><style>
li {
display : block;
background : lightblue;
padding:10px;
border-width:2px;
border-color:black;
border-style:solid;
}
</style>
ul<>
<li>First Element</li>
<li>Second Element</li>
<li>Third Element</li>
</ul>
<!−-Inline-block: unordered list−->
<style>
li {
display : inline-block;
background : lightblue;
padding:10px;
border-width:2px;
border-color:black;
border-style:solid;
}
</style>
<ul>
<li>First Element </li>
<li>Second Element </li>
<li>Third Element </li>
</ul>
An element that is given the none value to its display property will not be displayed at all.
For example let's create a div-element that has an id of myDiv:
<div id="myDiv"></div>
This can now be marked as not being displayed by the following CSS rule:
#myDiv {
display: none;
}
When an element has been set to be display:none; the browser ignores every other layout property for that specific element (both position and float). No box will be rendered for that element and its existence in html does not affect the position of following elements.
Note that this is different from setting the visibility property to hidden. Setting visibility: hidden; for an element would not display the element on the page but the element would still take up the space in the rendering process as if it would be visible. This will therefore affect how following elements are displayed on the page.
The none value for the display property is commonly used along with JavaScript to show or hide elements at will, eliminating the need to actually delete and re-create them.
<style>
table {
width: 100%;
}
</style>
<table>
<tr>
<td>
I'm a table
</td>
</tr>
</table>
You can do same implementation like this;
<style>
.table-div {
display: table;
}
.table-row-div {
display: table-row;
}
.table-cell-div {
display: table-cell;
}
</style>
<div class="table-div">
<div class="table-row-div">
<div class="table-cell-div">
I behave like a table now
</div>
</div>
</div>
Grid layout is a new and powerful CSS layout system that allows to divide a web page content into rows and columns in an easy way.
display grid / inline-grid
The CSS Grid is defined as a display property. It applies to a parent element and its immediate children only.
Consider the following markup:
<section class="container"> <div class="item1">item1</div> <div class="item2">item2</div> <div class="item3">item3</div> <div class="item4">item4</div> </section>
The easiest way to define the markup structure above as a grid is to simply set its display property to grid:
.container {
display: grid;
}
However, doing this will invariably cause all the child elements to collapse on top of one another. This is because the children do not currently know how to position themselves within the grid. But we can explicitly tell them.
First we need to tell the grid element .container how many rows and columns will make up its structure and we can do this using the grid-columns and grid-rows properties (note the pluralisation):
.container {
display: grid;
grid-columns: 50px 50px 50px;
grid-rows: 50px 50px;
}
However, that still doesn't help us much because we need to give an order to each child element. We can do this by specifying the grid-row and grid-column values which will tell it where it sits in the grid:
.container .item1 {
grid-column: 1;
grid-row: 1;
}
.container .item2 {
grid-column: 2;
grid-row: 1;
}
.container .item3 {
grid-column: 1;
grid-row: 2;
}
.container .item4 {
grid-column: 2;
grid-row: 2;
}
By giving each item a column and row value it identifies the items order within the container.
View a working example on Demo (jsFiddle). You'll need to view this in IE10, IE11 or Edge for it to work as these are currently the only browsers supporting Grid Layout (with vendor prefix -ms-) or enable a flag in Chrome, Opera and Firefox according to canIuse in order to test with them.
The table-layout property changes the algorithm that is used for the layout of a table.
Below an example of two tables both set to: width 150px:
The table on the left has table-layout: auto while the one on the right has table-layout: fixed. The former is wider than the specified width (210px instead of 150px) but the contents fit. The latter takes the defined width of 150px, regardless if the contents overflow or not.
| Value | Description |
|---|---|
| auto | This is the default value. It defines the layout of the table to |
| be determined by the contents of its' cells. | |
| fixed | This value sets the table layout to be determined by the width |
| property provided to the table. If the content fixed of a cell exceeds | |
| this width, the cell will not resize but instead, let the content overflow. |
The empty-cells property determines if cells with no content should be displayed or not. This has no effect unless border-collapse is set to separate.
Below an example with two tables with different values set to the empty-cells property:
The table on the left has empty-cells: show while the one on the right has empty-cells: hide. The former does display the empty cells whereas the latter does not.
| Value | Description |
|---|---|
| show | This is the default value. It shows cells even if they are empty. |
| hide | This value hides a cell altogether if there are no contents in the cell. |
The border-collapse property determines if a tables' borders should be separated or merged.
Below an example of two tables with different values to the border-collapse property:
The table on the left has border-collapse: separate while the
one on the right has
border-collapse: collapse.
| Value | Description |
|---|---|
| separate | This is the default value. It makes the borders of the table separate from each other. |
| collapse | This value sets the borders of the table to merge together, rather than being distinct. |
The border-spacing property determines the spacing between cells. This has no effect unless border-collapse is set to separate.
Below an example of two tables with different values to the border-spacing property:
The table on the left has border-spacing: 2px (default) while the one on the right has border-spacing: 8px.
| Value | Description |
|---|---|
| <length> | This is the default behavior, though the exact value can vary between browsers. |
| <length> <length> | This syntax allows specifying separate horizontal and vertical values respectively. |
The caption-side property determines the vertical positioning of the <caption> element within a table. This has no effect if such element does not exist.
Below an example with two tables with different values set to the caption-side property:
The table on the left has caption-side: top while the one on the right has caption-side: bottom.
| Value | Description |
|---|---|
| top | This is the default value. It places the caption above the table. |
| bottom | This value places the caption below the table. |
| Parameter | Details |
|---|---|
| transition-property | The specific CSS property whose value change needs to be transitioned (or) all, if all the |
| transitionable properties need to be transitioned. | |
| transition-duration | The duration (or period) in secdons (s) or milliseconds (ms) over which the transition |
| must take place. | |
| transition-timing-function | A function that describes how the intermediate values during the transition are |
| calculated. Commonly used values are ease, ease-in, ease-out, ease-in-out, linear, | |
| cubic-bezier(), steps(). More information about the various timing functions can be | |
| found in the W3C specs. | |
| transition-delary | The amount of time that must have elapsed before the transition can start. Can be |
| specified in seconds (s) or milliseconds (ms). |
div {
width: 150px;
height: 150px;
background-color: red;
transition: background-color 1s;
}
div:hover {
background-color: green;
}
<div></div>
This example will change the background color when the div is hovered the background-color change will last 1 second.
The cubic-bezier function is a transition timing function which is often used for custom and smooth transitions.
The function takes four parameters:
cubic-bezier(P1_x, P1_y, P2_x, P2_y)
These parameters will be mapped to points which are part of a Bézier curve:
For CSS Bézier Curves, P0 and P3 are always in the same spot. P0 is at (0,0) and P3 is at (1,1), which menas that the parameters passed to the cubic-bezier function can only be between 0 and 1.
If you pass parameters which aren't in this interval the function will default to a linear transition.
Since cubic-bezier is the most flexible transition in CSS, you can translate all other transition timing function to cubic-bezier functions:
linear:cubic-bezier(0,0,1,1) ease-in: cubic-bezier(0.42, 0.0, 1.0, 1.0) ease-out: cubic-bezier(0.0, 0.0, 0.58, 1.0) ease-in-out: cubic-bezier(0.42, 0.0, 0.58, 1.0)
div {
height: 100px;
width: 100px;
border: 1px solid;
transition-property: height, width;
transition-duration: 1s, 500ms;
transition-timing-function: linear;
transition-delay: 0s, 1s;
}
div: hover {
height: 200px;
width: 200px;
}
| Parameter | Details |
|---|---|
| property | Either the CSS property to transition on, or all, which specifies all transition-able |
| properties. | |
| duration | Transition time, either in seconds or milliseconds. |
| timing-function | Specifies a function to define how intermediate values for properties are computed. |
| Common values are ease, linear, and step-end. Check out the easing function cheat- | |
| sheet for more. | |
| delay | Amount of time, in seconds or milliseconds, to wait before playing the animation. |
For multi-stage CSS animations, you can create CSS @keyframes. Keyframes allow you to define multiple animation points, called a keyframe, to define more complex animations.
In this example, we'll make a basic background animation that cycles between all colors.
<span style="color:blue">@keyframes</span> rainbow-background {
0% { background-color: #ff0000; }
8.333% { background-color: #ff8000; }
16.667% { background-color: #ffff00; }
25.000% { background-color: #80ff00; }
33.333% { background-color: #00ff00; }
41.667% { background-color: #00ff80; }
50.000% { background-color: #00ffff; }
58.333% { background-color: #0080ff; }
66.667% { background-color: #0000ff; }
75.000% { background-color: #8000ff; }
83.333% { background-color: #ff00ff; }
91.667% { background-color: #ff0080; }
100.00% { background-color: #ff0000; }
}
.RainbowBackground {
animation: rainbow-background 5s infinite;
}
There's a few different things to note here. First, the actual @keyframes syntax.
@keyframes rainbow-background{
This sets the name of the animation to rainbow-background.
0% { background-color: #ff0000; }>
This is the definition for a keyframe within the animation. The first part, the 0% in the case, defines where the keyframe is during the animation. The 0% implies it is 0% of the total animation time from the beginning.
The animation will automatically transition between keyframes. So, by setting the next background color at 8.333%, the animation will smoothly take 8.333% of the time to transition between those keyframes.
.RainbowBackground {
animation: rainbow-background 5s infinite;
}
This code attaches our animation to all elements which have the .RainbowBackground class.
The actual animation property takes the following arguments;
In this particular example, both the 0% and 100% keyframes specify {; }. Wherever two or more keyframes share a state, one may specify them in a single statement. In this case, the two 0% and 100% lines could be replaced with this single line:
0%, 100% { background-color: #ff0000;}
For older WebKit-based browsers, you'll need to use the vendor prefix on both the @keyframes declaration and the animation property, like so:
@-webkit-keyframes{}
−webkit-animation: ...
Useful for simple animations, the CSS transition property allows number-based CSS properties to animate between states.
.Example {
height: 100px;
background: #fff;
}
.Example: hover {
height: 120px;
background: #ff0000;
}
By default, hovering over an element with the .Example class would immediately cause the element's height to jump to 120px and its background color to red (#ff0000).
By adding the transition property, we can cause these changes to occur over time:
.Example {
...
transition: all 400ms ease;
}
The all value applies the transition to all compatible (numbers-based) properties. Any compatible property name (such as height or top) can be substituted for this keyword.
400ms specifies the amount of time the transition takes. In this case, the element's change in height will take 400 milliseconds to complete.
Finally, the value ease is the animation function, which determines how the animation is played. ease means start slow, speed up, then end slow again. Other values are linear, ease-out, and ease-in.
The transition property is generally well-supported across all major browsers, excepting IE 9. For earlier versions of Firefox and Webkit-based browsers, use vendor prefixes like so:
.Example {
transition: all 400ms ease;
-moz-transition: all 400ms ease;
-webkit-transition: all 400ms ease;
}
Note: The transition property can animate changes between any two numerical values, regardless of unit. It can also transition between units, such as 100px to 50vh. However, it cannot transition between a number and a default or automatic value, such as transitioning an element's height from 100px to auto.
Our first syntax example shows the animation shorthand property using all of the available properties/parameters:
animation: 3s ease-in 1s 2 reverse both paused slidein; /* duration | timing-function | delay | iteration-count | direction | fill-mode | play- state | name */
Our second example is a little more simple, and shows that some properties can be omitted:
animation: 3s linear 1s slidein; /* duration | timing-function | delay | name */
Our third example shows the most minimal declaration. Note that the animation-name and animation-duration must be declared:
animation: 3s slidein; /* duration | name */
It's also worth mentioning that when using the animation shorthand the order of the properties makes a difference. Obviously the browser may confuse your duration with your delay.
If brevity isn't your thing, you can also skip the shorthand property and write out each property individually:
animation-duration: 3s; animation-timing-function: ease-in; animation-delay: 1s; animation-iteration-count: 2; animation-direction: reverse; animation-fill-mode: both; animation-play-state: paused; animation-name: slidein;
When creating animations and other GPU-heavy actions, it's important to understand the will-change attribute.
Both CSS keyframes and the transition property use GPU acceleration. Performance is increased by offloading calculations to the device's GPU. This is done by creating paint layers (parts of the page that are individually rendered) that are offloaded to the GPU to be calculated. The will-change property tells the browser what will animate, allowing the browser to create smaller paint areas, thus increasing performance.
The will-change property accepts a comma-separated list of properties to be animated. For example, if you plan on transforming an object and changing its opacity, you would specify:
.Example {
...
will-change: transform, opacity;
}
Note: Use will-change sparingly. Setting will-change for every element on a page can cause performance problems, as the browser may attempt to create paint layers for every element, significantly increasing the amount of processing done by the GPU.
| Function/Parameter | Details |
|---|---|
| rotate(x) | Defines a transformation that moves the element around a fixed point on the Z axis. |
| translate(x,y) | Moves the position of the element on the X and Y axis. |
| translateX(x) | Moves the position of the element on the X axis. |
| translateY(y) | Moves the position of the element on the Y axis. |
| scale(x,y) | Modifies the size of the element on the X and Y axis. |
| scaleX(x) | Modifies the size of the element on the X axis. |
| scaleY(y) | Modifies the size of the element on the Y axis. |
| skew(x,y) | Shear mapping, or transvection, distorting each point of an element by a certain angle in |
| each direction. | |
| skewX(x) | Horizontal shear mapping distorting each point of an element by a certain angle in the |
| horizontal direction. | |
| skewY(y) | Vertical shear mapping distorting each point of an element by a certain angle in the vertical |
| direction. | |
| matrix() | Defines a 2D transformation in the form of a transformation matrix. |
| angle | The angle by which the element should be rotated or skewed (depending on the function |
| with which it is used). Angle can be provided in degrees (deg), gradians (grad), radians (rad) | |
| or turns (turn). In skew () function, the second angle is optional. If not provided, there will be | |
| no (0) skew in Y-axis. | |
| length-or-percentage | The distance expressed as a length or percentage by which the element should be |
| translated. In translate () function, the second length-or-percentage is optional. If not | |
| provided, then there would be no (0) translation in Y-axis. | |
| scale-factor | A number which defines how many times the element should be scaled in the specified axis. |
| In scale function, the second scale-factor is optional. If not provided, the first scale-factor | |
| will be applied for Y-axis also. |
<div class="rotate"></div>
.rotate {
width: 100px;
height: 100px;
background: teal;
transform: rotate (45deg);
}
This example will rotate the div by 45 degrees clockwise. The center of rotation is in the center of the div, 50% from left and 50% from top. You can change the center of rotation by setting the transform-origin property.
transform-origin: 100% 50%;
The above example will set the center of rotation to the middle of the right side end.
<div class="scale"></div>
.scale {
width: 100px;
height: 100px;
background: teal;
transform: scale (0.5, 1.3);
}
This example will scale the div to 100px * 0.5 = 50px on the X axis and to 100px * 1.3 = 130px on the Y axis.
The center of the transform is in the center of the div, 50% from left and 50% from top.
<div class="skew"></div>
.skew {
width: 100px;
height: 100px;
background: teal;
transform: skew (20deg, -30deg);
}
This example will skew the div by 20 degrees on the X axis and by − 30 degrees on the Y axis. The center of the transform is in the center of the div, 50% from left and 50% from top.
Multiple transforms can be applied to an element in one property like this:
transform: rotate(15deg) translateX(200px);
This will rotate the element 15 degrees clockwise and then translate it 200px to the right.
In chained transforms, the coordinate system moves with the element. This means that the translation won't be horizontal but on an axis rotate 15 degrees clockwise as shown in the following image:
Changing the order of the transforms will change the output. The first example will be different to
transform: translateX(200px) rotate(15deg);
<div class="transform"></div>
.transform {
transform: rotate(15deg) translateX(200px);
}
As shown in this image:
<div class="translate"></div>
.translate {
width: 100px;
height: 100px;
background: teal;
transform: translate (200px, 50%);
}
This example will move the div by 200px on the X axis and by 100px * 50% = 50px on the Y axis.
You can also specify translations on a single axis.
On the X axis:
.translate {
transform: translateX(200px);
}
On the Y axis:
.translate {
transform: translateY(50%);
}
Transformations are done with respect to a point which is defined by the transform-origin property.
The property takes 2 values: transform-origin: X Y;
In the following example the first div (.tl) is rotate around the top left corner with transform-origin: 0 0; and the second (.tr) is transformed around it's top right corner with transform-origin: 100% 0. The rotation is applied on hover:
<div class="transform originl"></div> <div class="transform origin2"></div>
.transform {
display: inline-block;
width: 200px;
height: 100px;
background: teal;
transition: transform 1s;
}
.origin1 {
transform-origin: 0 0;
}
.origin2 {
transform-origin: 100% 0;
}
.transform: hover {
transform: rotate(30deg);
}
The default value for the transform-origin property is 50% 50% which is the center of the element.
div.needle {
margin:100px;
height:150px;
width:150px;
transform:rotateY(85deg) rotateZ(45deg);
/* presentational */
background-image: linear-gradient(to top left, #555 0%, #555 40%, #444 50%, #333 97%);
box-shadow:inset 6px 6px 22px 8px #272727;
}
<div class='needle'></div>
In the above example, a needle or compass pointer shape is created using 3D transforms. Generally when we apply the rotate transform on an element, the rotation happens only in the Z-axis and at best we will end up with diamond shapes only. But when a rotateY transform is added on top of it, the element gets squeezed in the Y-axis and thus ends up looking like a needle. The more the rotation of the Y-axis the more squeezed the element looks.
The output of the above example would be a needle resting on its tip. For creating a needle that is resting on its base, the rotation should be along the X-axis instead of along Y-axis. So the transform property's value would have to be something like rotate(85deg) rotateZ(45deg);.
This CodePen uses a similar approach to create something that resembles the Safari logo or a compass dial.
<div id="title"> <h1 data-content="HOVER">HOVER</h1> </div>
*{margin:0;padding:0;}
html,body{height:100%;width:100%;overflow:hidden;background:#0099CC;}
#title {
position: absolute;
top: 50%; left:50%;
transform: translate(-50%,-50%);
perspective-origin:50%50%;
perspective:300px;
}
h1 {
text-align:center;
font-size:12vmin;
font-family:'Open Sans', sans-serif;
color:rgba(0,0,0,0.8);
line-height:1em;
transform:rotateY(50deg);
perspective:150px;
perspective-origin:0% 50%;
}
h1:after {
content:attr(data-content);
position:absolute;
left:0; top:0;
transform-origin:50%100%;
transform:rotateX(-90deg);
color:#0099CC;
}
#title:before {
content:'';
position:absolute;
top:-150%; left:-25%;
width:180%; height:328%;
background:rgba(255,255,255,0.7);
transform-origin:0 100%;
transform:translatez(-200px) rotate(40deg) skewX(35deg);
border-radius:0 0 100% 0;
}
View example with additional hover effect (CodePen).
In this example, the text is transformed to make it look like it is going into the screen away from the user.
The shadow is transformed accordingly so it follows the text. As it is made with a pseudo element and the data attribute, it inherits the transforms form it's parent (the H1 tag).
The white "light" is made with a pseudo element on the #title element. It is skewed and uses border-radius for the rounded corner.
The backface-visibility property relates to 3D transforms.
With 3D transforms and the backface-visibility property, you're able to rotate an element such that the original front of an element no longer faces the screen.
For example, this would flip an element away from the screen:
<div class="flip">Loren ipsum</div>
<div class="flip back">Lorem ipsum</div>
.flip {
-webkit-transform: rotateY(180deg);
-moz-transform: rotateY(180deg);
-ms-transform: rotateY(180deg);
-webkit-backface-visibility: visible;
-moz-backface-visibility: visible;
-ms-backface-visibility: visible;
}
.flip.back {
-webkit-backface-visibility: hidden;
-moz-backface-visibility: hidden;
-ms-backface-visibility: hidden;
}
Firefox 10+ and IE 10+ support backface-visibility without a prefix. Opera, Chrome, Safari, iOS, and Android all need -webkit-backface-visibility.
It has 4 values:
3D transforms can be use to create many 3D shapes. Here is a simple 3D CSS cube example:
<div class="cube"> <div class="cubeFace"></div> <div class="cubeFace face2"></div> </div>
body {
perspective-origin: 50% 100%;
perspective: 1500px;
overflow: hidden;
}
.cube {
position: relative;
padding-bottom: 20%;
transform-style: preserve-3d;
transform-origin: 50% 100%;
transform: rotateY(45deg) rotateX(0);
}
.cubeFace {
position: absolute;
top: 0;
left: 40%
width: 20%
height: 100%
margin: 0 auto;
transform-style: inherit;
background: #C53329;
box-shadow: inset 0 0 0 5px #333;
transform-origin: 50% 50%;
transform: rotateX(90deg);
backface-visibility: hidden;
}
.face2 {
transform-origin: 50% 50%;
transform: rotatez(90deg) translateX(100%) rotateY(90deg);
}
.cubeFace:before, cubeFace:after {
content: ''
position: absolute;
width: 100%;
height: 100%;
transform-origin: 0 0;
background: inherit;
box-shadow: inherit;
backface-visibility: inherit;
}
.cubeFace:before {
top: 100%;
left: 0;
transform: rotateX(−90deg);
}
.cubeFace:after {
top: 0;
left: 100%;
transform: rotateY(90deg);
}
View this example (CodePen).
Additional styling is added in the demo and a transform
is applied on hover to view the 6 faces of the cube.
Should be noted that:
| Value | Description |
|---|---|
| blur(x) | Blurs the image by x pixels. |
| brightness(x) | Brightens the image at any value above 1.0 or 100%. Below that, the image will be |
| darkened. | |
| contrast(x) | Provides more contrast to the image at any value above 1.0 or 100%. Below that, the |
| image will get less saturated. | |
| drop-shadow(h,v,x,y,z) | Gives the image a drop-shadow. h and v can have negative values. x, y, and z are optional. |
| greyscale(x) | Shows the image in greyscale, with a maximum value of 1.0 or 100%. |
| hue-rotate(x) | Applies a hue-rotation to the image. |
| invert(x) | Inverts the color of the image with a maximum value of 1.0 or 100%. |
| opacity(x) | Sets how opaque/transparent the image is with a maximum value of 1.0 or 100%. |
| saturate(x) | Saturates the image at any value above 1.0 or 100%. Below that, the image will start to |
| de-saturate. | |
| sepia(x) | Converts the image to sepia with a maximum value of 1.0 or 100%. |
<img src='donald-duck.png' alt='Donald Duck' title='Donald Duck' />
img {
-webkit-filter: blur(1px);
filter: blur(1px);
}
<p>My shadow always follows me.</p>
p {
-webkit-filter: drop-shadow(10px 10px 1px green);
filter: drop-shadow(10px 10px 1px green);
}
<img src='donald-duck.png' alt='Donald Duck' title='Donald Duck' />
img {
-webkit-filter: hue-rotate(120deg);
filter: hue-rotate(120deg);
}
To use multiple filters, separate each value with a space.
<img src='donald-duck.png' alt='Donald Duck' title='Donald Duck' />
img {
-webkit-filter: brightness(200%) grayscale(100%) sepia(100%) invert(100%);
filter: brightness(200%) grayscale(100%) sepia(100%) invert(100%);
}
<div></div>
div {
width: 100px;
height: 100px;
background-color: white;
-webkit-filter: invert(100%);
filter: invert(100%);
}
Turns from white to black.
| Value | Description |
|---|---|
| none | No cursor is rendered for the element. |
| auto | Default. The browser sets a cursor. |
| help | The cursor indicates that help is available. |
| wait | The cursor indicates that the program is busy. |
| move | The cursor indicates something is to be moved. |
| pointer | The cursor is a pointer and indicates a link. |
The pointer-events property allows for control over how HTML elements respond to mouse/touch events.
.disabled {
pointer-events: none;
}
'none' prevents all click, state and cursor options on the specified HTML element.
The caret-color CSS property specifies the color of the caret, the visible indicator of the insertion point in an element where text and other content is inserted by the user's typing or editing.
<input id="example"/>
#example {
caret-color: red;
}
| Parameters | Details |
|---|---|
| inset | by default, the shadow is treated as a drop shadow. the inset keyword draws the shadow inside the |
| frame/border. | |
| offset-x | the horizontal distance. |
| offset-y | the vertical distance. |
| blur-radius | 0 by default. Value cannot be negative. the bigger the value, the bigger and lighter the shadow |
| becomes. | |
| spread-radius | 0 by default. Positive values will cause the shadow to expand. Negative values will cause the shadow |
| to shrink. | |
| color | can be various notations: a color keyword, hexadecimal, rgb(), rgba(), hsla(). |
<div class="box_shadow"></div>
.box_shadow {
background-color: #1C90F3;
width: 200px;
height: 100px;
margin: 50px;
}
.box_shadow:after {
content: "";
width: 190px;
height: 1px;
margin-top: 98px;
margin-left: 5px;
display: block;
position: absolute;
z-index: −1;
-webkit-box-shadow: 0px 0px 8px 2px #444444;
-moz-box-shadow: 0px 0px 8px 2px #444444;
box-shadow: 0px 0px 8px 2px #444444;
}
<div class="box_shadow"></div>
.box_shadow {
-webkit-box-shadow: 0px 0px 10px -1px #444444;
-moz-box-shadow: 0px 0px 10px -1px #444444;
box-shadow: 0px 0px 10px -1px #444444;
}
<div class="box_shadow"></div>
.box_shadow {
background-color: #1C90F3;
width: 200px;
height: 100px;
margin: 50px;
-webkit-box-shadow: inset 0px 0px 10px 0px #444444;
-moz-box-shadow: inset 0px 0px 10px 0px #444444;
box-shadow: inset 0px 0px 10px 0px #444444;
}
<div class="box_shadow"></div>
.box_shadow {
width: 100px;
height: 100px;
margin: 100px;
box-shadow: -52px -52px 0px 0px #f65314,
52px -52px 0px 0px #7cbb00,
-52px 52px 0px 0px #00a1f1,
52px 52px 0px 0px #ffbb00;
}
| Parameter | Details |
|---|---|
| none | A value of none means that the float area (the area that is used for wrapping content around a float |
| element) is unaffected. This is the default/initial value. | |
| basic-shape | Refers to one among inset(), circle(), ellipse() or polygon(). Using one of these functions and its |
| values the shape is defined. | |
| shape-box | Refers to one among margin-box, border-box, padding-box, content-box. When only <shape-box> is |
| provided (without <basic-shape>) this box is the shape. When it is used along with <basic-shape>, this | |
| acts as the reference box. | |
| image | When an image is provided as value, the shape is computed based on the alpha channel of the image image |
| specified. |
With the shape-outside CSS property one can define shape values for the float area so that the inline content wraps around the shape instead of the float's box.
img: nth-of-type (1) {
shape-outside: circle (80px at 50% 50%);
float: left;
width: 200px;
}
img: nth-of-type (2) {
shape-outside: circle (80px at 50% 50%);
float: right;
width: 200px;
}
p {
text-align: center;
line-height: 30px; /* purely for demo */
}
<img src="http://images.clipartpanda.com/circle-clip-art-circlergb.jpg"> <img src="http://images.clipartpanda.com/circle-clip-art-circlergb.jpg"> <p>Some paragraph whose text content is required to be wrapped such that it follows the curve of the circle on either side. And then there is some filler text just to make the text long enough. Lorem Ipsum Dolor Sit Amet....</p>
In the above example, both the images are actually square images and when the text is placed without the shapeoutside property, it will not flow around the circle on either side. It will flow around the containing box of the image only. With shape-outside the float area is re-defined as a circle and the content is made to flow around this imaginary circle that is created using shape-outside.
The imaginary circle that is used to re-define the float area is a circle with radius of 80px drawn from the center-mid point of the image's reference box.
Below are a couple of screenshots to illustrate how the content would be wrapped around when shape-outside is used and when it is not used.
The shape-margin CSS property adds a margin to shape-outside.
img:nth-of-type(1) {
shape-outside: circle(80px at 50% 50%);
shape-margin: 10px;
float: left;
width: 200px;
}
img:nth-of-type(2) {
shape-outside: circle(80px at 50% 50%);
shape-margin: 10px;
float: right;
width: 200px;
}
p {
text-align: center;
line-height: 30px; /* purely for demo */
}
<img src="http://images.clipartpanda.com/circle-clip-art-circlergb.jpg"> <p><img src="http://images.clipartpanda.com/circle-clip-art-circlergb.jpg"> <p>Some paragraph whose text content is required to be wrapped such that it follows the curve of the circle on either side. And then there is some filler text just to make the text long enough. Lorem Ipsum Dolor Sit Amet....</p>
In this example, a 10px margin is added around the shape using shape-margin. This creates a bit more space between the imaginary circle that defines the float area and the actual content that is flowing around.
| Value | Description |
|---|---|
| list-style-type | the type of list-item marker. |
| list-style-position | specifies where to place the marker. |
| list-style-image | specifies the type of list-item marker. |
| initial | sets this property to its default value. |
| inherit | inherits this property from its parent element., |
A list consists of <li> elements inside a containing element (<ul> or <ol>). Both the list items and the container can have margins and paddings which influence the exact position of the list item content in the document. The default values for the margin and padding may be different for each browser. In order to get the same layout cross- browser, these need to be set specifically.
Each list item gets a 'marker box', which contains the bullet marker. This box can either be placed inside or outside of the list item box.
list-style-position: inside;
places the bullet within the <li> element, pushing the content to the right as needed.
list-style-position: outside;
places the bullet left of the <li> element. If there is not enough space in the padding of the containing element, the marker box will extend to the left even if it would fall off the page.
Showing the result of inside and outside positioning: Demo (jsFiddle).
Sometimes, a list should just not display any bullet points or numbers. In that case, remember to specify margin and padding.
<ul> <li>first item</li> <li>second item</li> </ul>
ul {
list-style-type: none;
}
li {
margin: 0;
padding: 0;
}
Specific for <li> tags within an unordered list (<ul>);
list-style: disc; /* A filled circle (default) */ list-style: circle; /* A hollow circle */ list-style: square; /* A filled square */ list-style: '-'; /* any string */
Specific for <li> tags within an ordered list (<ol>);
list-style: decimal; /* Decimal numbers beginning with 1 (default) */ list-style: decimal-leading-zero; /* Decimal numbers padded by initial zeros (01, 02, 03,* ... *10) */ list-style: lower-roman; /* Lowercase roman numerals (i., ii., iii., iv., ...) */ list-style: upper-roman; /* Uppercase roman numerals (I., II., III., IV., ...) */ list-style-type: lower-greek; /* Lowercase roman letters (*α*.,* β*.,* γ*.,* δ*., ...) */ list-style-type: lower-alpha; /* Lowercase letters (a., b., c., d., ...) */ list-style-type: lower-latin; /* Lowercase letters (a., b., c., d., ...) */ list-style-type: upper-alpha; /* Uppercase letters (A., B., C., D., ...) */ list-style-type: upper-latin; /* Uppercase letters (A., B., C., D., ...) */
Non-specific:
list-style: none; /* No visible list marker */ list-style: inherit; /* Inherits from parent */
| Parameter | Details |
|---|---|
| counter-name | This is the name of the counter that needs to be created or incremented or printed. It can be any custom name as the developer wishes. |
| integer | This integer is an optional value that when provided next to the counter name will represent the initial value of the counter (in counter-set, counter-reset properties) or the value by which the counter should be incremented (in counter-increment). |
| none | This is the initial value for all 3 counter-* properties. When this value is used for counter-increment, the value of none of the counters are affected. When this is used for the other two, no counter is created. |
| counter-style | This specifies the style in which the counter value needs to be displayed. It supports all values supported by the list-style-type property. If none is used then the counter value is not printed at all. |
| connector-string | This represents the string that must be placed between the values of two different counter levels (like the "." in "2.1.1"). |
body {
counter-reset: item-counter;
}
.item {
counter-increment: item-counter;
}
.item: before {
content: counter (item-counter, upper-roman) ". "; /* by specifying the upper-roman as style the
output would be in roman numbers */
}
<div class='item'>Item No: 1</div> <div class='item'>Item No: 2</div> <div class='item'>Item No: 3</div>
In the above example, the counter's output would be displayed as I, II, III (roman numbers) instead of the usual 1, 2, 3 as the developer has explicitly specified the counter's style.
body {
counter-reset: item-counter; /* create the counter */
}
.item {
counter-increment: item-counter; /* increment the counter every time an element with class "item" is encountered */
}
.item-header: before {
content: counter (item-counter)". "; /* print the value of the counter before the header and
append a "." to it */
}
/* just for demo */
.item {
border: 1px solid;
height: 100px;
margin-bottom: 10px;
}
.item-header {
border-bottom: 1px solid;
height: 40px;
line-height: 40px;
padding: 5px;
}
.item-content {
padding: 8px;
}
<div class='item'> <div class='item-header'>Item 1 Header</div> <div class='item-content'>Lorem Ipsum Dolor Sit Amet....</div> </div> <div class='item'> <div class='item-header'>Item 2 Header</div> <div class='item-content'>Lorem Ipsum Dolor Sit Amet....</div> </div> <div class='item'> <div class='item-header'>Item 3 Header</div> <div class='item-content'>Lorem Ipsum Dolor Sit Amet....</div> </div>
The above example numbers every "item" in the page and adds the item's number before its header (using content property of .item-header element's pseudo). A live demo of this code (jsFiddle).
ul {
list-style: none;
counter-reset: list-item-number; /* self nesting counter as name is same for all levels */
}
li {
counter-increment: list-item-number;
}
li: before {
content: counters (list-item-number, ".")" "; /* usage of counters() function means value of
counters at all higher levels are combined before printing */
}
<ul>
<li>Level 1
<ul>
<li>Level 1.1
<ul>
<li>Level 1.1.1</li>
</ul>
</li>
</ul>
</li>
<li>Level 2
<ul>
<li>Level 2.1
<ul>
<li>Level 2.1.1</li>
<li>Level 2.1.2</li>
</ul>
</li>
</ul>
</li>
<li>Level 3</li>
</ul>
The above is an example of multi-level numbering using CSS counters. It makes use of the self-nesting concept of counters. Self nesting is a concept where if an element already has a counter with the given name but is having to create another then it creates it as a child of the existing counter. Here, the second level ul already inherits the list-item-number counter from its parent but then has to create its own list-item-number (for its children li) and so creates (counter for first level). Thus it achieves the multi-level numbering.
The output is printed using the counters() function instead of the counter() function because the counters() function is designed to prefix the value of all higher level counters (parent) when printing the output.
Accepts a mathematical expression and returns a numerical value.
It is especially useful when working with different types of units (e.g. subtracting a px value from a percentage) to calculate the value of an attribute.
+, -, /, and * operators can all be used, and parentheses can be added to specify the order of operations if necessary.
Use calc() to calculate the width of a div element:
#div1 {
position: absolute;
left: 50px;
width: calc (100% − 100px);
border: 1px solid black;
background-color: yellow;
padding: 5px;
text-align: center;
}
Use calc() to determine the position of a background-image:
background-position: calc (50%+ 17px) calc (50%+ 10px), 50% 50%;
Use calc() to determine the height of an element:
Returns the value of an attribute of the selected element.
Below is a blockquote element which contains a character inside a data-* attribute which CSS can use (e.g. inside the ::before and ::after pseudo-element) using this function.
<blockquote data-mark='"'></blockquote>
In the following CSS block, the character is appended before and after the text inside the element:
blockquote[data-mark]::before,
blockquote[data-mark]::after {
content: attr(data-mark);
}
The var() function allows CSS variables to be accessed.
/* set a variable */
:root {
−- primary-color: blue;
}
/* access variable */
selector{
color: var (−-primary-color);
}
This feature is currently under development. Check CanIuse.com for the latest browser support.
Creates an image representing a gradient of colors radiating from the center of the gradient
radial-gradient(red, orange, yellow) /* A gradient coming out from the middle of the gradient, red at the center, then orange, until it is finally yellow at the edges */
Creates a image representing a linear gradient of colors.
linear-gradient( 0 deg, red, yellow 50%, blue);
This creates a gradient going from bottom to top, with colors starting at red, then yellow at 50%, and finishing in blue.
CSS Variables allow authors to create reusable values which can be used throughout a CSS document.
For example, it's common in CSS to reuse a single color throughout a document. Prior to CSS Variables this would mean reusing the same color value many times throughout a document. With CSS Variables the color value can be assigned to a variable and referenced in multiple places. This makes changing values easier and is more semantic than using traditional CSS values.
:root {
−-red: #b00;
−-blue: #4679bd;
−- grey: #ddd;
}
.Bx1 {
color: var (−- red);
background: var(−- grey);
border: 1px solid var (−- red);
}
:root {
−-W200: 200px;
−- W 10: 10px;
}
.Bx2 {
width: var (−-W200);
height: var (−-W200);
margin: var (−- W 10);
}
CSS variables cascade in much the same way as other properties, and can be restated safely.
You can define variables multiple times and only the definition with the highest specificity will apply to the element selected.
Assuming this HTML:
<a class="button">Button Green</a> <a class="button button_red">Button Red</a> <a class="button">Button Hovered On</a>
We can write this CSS:
.button {
−- color: green;
padding: .5rem;
border: 1px solid var (−- color);
color: var (−- color);
}
.button: hover {
−- color: blue;
}
.button_red {
−- color: red;
}
Naming When naming CSS variables, it contains only letters and dashes just like other CSS properties (eg: lineheight, -moz-box-sizing) but it should start with double dashes (−-)
// These are Invalids variable names −-123color: blue; −-# color: red; −-bg_ color: yellow −-$ width: 100px; // Valid variable names −− color: red; −− bg-color: yellow −− width: 100px;
/* The variable names below are all different variables */ −-pcolor: ; −-Pcolor: ; −-pColor: ;
/* Invalid */ −-color:; /* Valid */ −-color:; /* space is assigned */
/* Invalid - CSS doesn't support concatenation */
.logo{
−-logo-url: 'logo';
background: url('assets/img/' var(−-logo-url) '.png');
}
/* Invalid - CSS bug */
.logo{
−-logo-url: 'assets/img/logo.png';
background: url(var(−-logo-url));
}
/* Valid */
.logo{
−-logo-url: url('assets/img/logo.png');
background: var(−-logo-url);
}
/* Invalid */ −-width: 10; width: var(−-width)px; /* Valid */ −-width: 10px; width: var(−-width); /* Valid */ −-width:10; width: calc(1px * var(−-width)); /* multiply by 1 unit to convert */ width: calc(1em * var(−-width));
You can re-set variables within media queries and have those new values cascade wherever they are used, something that isn't possible with pre-processor variables.
Here, a media query changes the variables used to set up a very simple grid:
<div></div> <div></div> <div></div> <div></div>
:root{
−-width: 25%;
−-content: 'This is desktop';
}
@media only screen and (max-width: 767px){
:root{
−-width: 50%;
−-content: 'This is mobile';
}
}
@media only screen and (max-width: 480px){
:root{
−-width: 100%;
}
}
div {
width: calc(var(−-width) − 20px);
height: 100px;
}
div: before{
content: var(−-content);
}
/* Other Styles */
body {
padding: 10px;
}
div {
display: flex;
align-items: center;
justify-content: center;
font-weight: bold;
float: left;
margin: 10px;
border: 4px solid black;
background: red;
}
You can try resizing the window in this Demo (CodePen).
Here's an animated screenshot of the resizing in action:
A trapezoid can be made by a block element with zero height (height of 0px), a width greater than zero and a border, that is transparent except for one side:
<div class="trapezoid"></div>
.trapezoid {
width: 50px;
height: 0;
border-left: 50px solid transparent;
border-right: 50px solid transparent;
border-bottom: 100px solid black;
}
With changing the border sides, the orientation of the trapezoid can be adjusted.
To create a CSS triangle define an element with a width and height of 0 pixels. The triangle shape will be formed using border properties. For an element with 0 height and width the 4 borders (top, right, bottom, left) each form a triangle. Here's an element with 0 height/width and 4 different colored borders.
By setting some borders to transparent, and others to a color we can create various triangles. For example, in the Up triangle, we set the bottom border to the desired color, then set the left and right borders to transparent. Here's an image with the left and right borders shaded slightly to show how the triangle is being formed.
The dimensions of the triangle can be altered by changing the different border widths - taller, shorter, lopsided, etc. The examples below all show a 50x50 pixel triangle.
<div class="triangle-up"></div>
.triangle-up {
width: 0;
height: 0;
border-left: 25px solid transparent;
border-right: 25px solid transparent;
border-bottom: 50px solid rgb(246, 156, 85);
}
<div class="triangle-down"></div>
.triangle-down {
width: 0;
height: 0;
border-left: 25px solid transparent;
border-right: 25px solid transparent;
border-top: 50px solid rgb(246, 156, 85);
}
<div class="triangle-right"></div>
.triangle-right {
width: 0;
height: 0;
border-top: 25px solid transparent;
border-bottom: 25px solid transparent;
border-left: 50px solid rgb(246, 156, 85);
}
<div class="triangle-left"></div>
.triangle-left {
width: 0;
height: 0;
border-top: 25px solid transparent;
border-bottom: 25px solid transparent;
border-right: 50px solid rgb(246, 156, 85);
}
Triangle - Pointing Up/Right
<div class="triangle-up-right"></div>
.triangle-up-right {
width: 0;
height: 0;
border-top: 50px solid rgb(246, 156, 85);
border-left: 50px solid transparent;
}
<div class="triangle-up-left"></div>
.triangle-up-left {
width: 0;
height: 0;
border-top: 50px solid rgb(246, 156, 85);
border-right: 50px solid transparent;
}
<div class="triangle-down-right"></div>
.triangle-down-right {
width: 0;
height: 0;
border-bottom: 50px solid rgb(246, 156, 85);
border-left: 50px solid transparent;
}
<div class="triangle-down-left"></div>
.triangle-down-left {
width: 0;
height: 0;
border-bottom: 50px solid rgb(246, 156, 85);
border-right: 50px solid transparent;
}
To create a circle, define an element with an equal width and height (a square) and then set the border-radius property of this element to 50%.
<div class="circle"></div>
.circle {
width: 50px;
height: 50px;
background: rgb(246, 156, 85);
border-radius: 50%;
}
An ellipse is similar to a circle, but with different values for width and height.
<div class="oval"></div>
.oval {
width: 50px;
height: 80px;
background:rgb(246, 156, 85);
border-radius: 50%;
}
A burst is similar to a star but with the points extending less distance from the body. Think of a burst shape as a square with additional, slightly rotated, squares layered on top.
The additional squares are created using the ::before and ::after psuedo-elements.
An 8 point burst are 2 layered squares. The bottom square is the element itself, the additional square is created using the :before pseudo-element. The bottom is rotated 20°, the top square is rotated 135°.
<div class="burst-8"></div>
.burst-8 {
background: rgb(246, 156, 85);
width: 40px;
height: 40px;
position: relative;
text-align: center;
-ms-transform: rotate(20deg);
transform: rotate(20eg);
}
.burst-8::before {
content: "";
position: absolute;
top: 0;
left: 0;
height: 40px;
width: 40px;
background: rgb(246, 156, 85);
-ms-transform: rotate(135deg);
transform: rotate(135deg);
}
An 12 point burst are 3 layered squares. The bottom square is the element itself, the additional squares are created using the :pseudo-elements. The bottom is rotated 0°, the next square is rotated 30°, and the top is rotated 60°.
<div class="burst-12"></div>
.burst-12 {
width: 40px;
height: 40px;
position: relative;
text-align: center;
background: rgb(246, 156, 85);
}
.burst-12::before, .burst-12::after {
content: "";
position: absolute;
top: 0;
left: 0;
height: 40px;
width: 40px;
background: rgb(246, 156, 85);
}
.burst-12::before {
-ms-transform: rotate(30deg);
transform: rotate(30deg);
}
.burst-12::after {
-ms-transform: rotate(60deg);
transform: rotate(60deg);
}
To create a square, define an element with both a width and height. In the example below, we have an element with a width and height of 100 pixels each.
<div class="square"></div>
.square {
width: 100px;
height: 100px;
background: rgb(246, 156, 85);
}
skewX () and skewY
This example shows how to create a cube using 2D transformation methods () on pseudo elements.
<div class="cube"></div>
.cube {
background: #dc2e2e;
width: 100px;
height: 100px;
position: relative;
margin: 50px;
}
.cube::before {
content: '';
display: inline-block;
background: #f15757;
width: 100px;
height: 20px;
transform: skewX(-40deg);
position: absolute;
top: -20px;
left: 8px;
}
.cube::after {
content: '';
display: inline-block;
background: #9e1515;
width: 16px;
height: 100px;
transform: skewY(-50deg);
position: absolute;
top: -10px;
left: 100%;
}
This example shows how to create a pyramid using borders and 2D transformation methods skew() and rotate() on pseudo elements.
<div class="pyramid"></div>
.pyramid {
width: 100px;
height: 200px;
position: relative;
margin: 50px;
}
.pyramid::before,.pyramid::after {
content: '';
display: inline-block;
width: 0;
height: 0;
border: 50px solid;
position: absolute;
}
.pyramid::before {
border-color: transparent transparent #ff5656 transparent;
transform: scaleY(2) skewY(-40deg) rotate(45deg);
}
.pyramid::after {
border-color: transparent transparent #d64444 transparent;
transform: scaleY(2) skewY(40deg) rotate(-45deg);
}
The CSS multi-column layout makes it easy to create multiple columns of text.
<div id="multi-columns">Lorem ipsum dolor sit amet,
consectetur adipisicing elit, sed do eiusmod tempor incididunt ut
labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud
exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum
dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est
laborum</div>
.multi-columns {
-moz-column-count: 2;
-webkit-column-count: 2;
column-count: 2;
}
The column-width property sets the minimum column width. If column-count is not defined the browser will make as many columns as fit in the available width.
<div id="multi-columns">
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do
eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad
minim veniam, quis nostrud exercitation ullamco laboris nisi ut
aliquip ex ea commodo consequat. Duis aute irure dolor in
reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla
pariatur. Excepteur sint occaecat cupidatat non proident, sunt in
culpa qui officia deserunt mollit anim id est laborum
</div>
.multi-columns {
-moz-column-width: 100px;
-webkit-column-width: 100px;
column-width: 100px;
}
CSS allows to define that element contents wrap into multiple columns with gaps and rules between them.
<div class="content"> Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. Nam liber tempor cum soluta nobis eleifend option congue nihil imperdiet doming id quod mazim placerat facer possim assum. </div>
.content {
−webkit-column-count: 3; /* Chrome, Safari, Opera */
−moz-column-count: 3; /* Firefox */
column-count: 3;
}
Consider the following HTML markup:
<section> <p>Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum.</p> <p> Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p> <p>Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p> </section>
With the following CSS applied the content is split into three columns separated by a gray column rule of two pixels.
section {
columns: 3;
column-gap: 40px;
column-rule: 2px solid gray;
}
See a live sample of this (jsFiddle).
The horizontally justified navigation (menu) bar has some number of items that should be justified. The first (left) item has no left margin within the container, the last (right) item has no right margin within the container. The distance between items is equal, independent on the individual item width.
<nav>
<ul>
<li>abc</li>
<li>abcdefghijkl</li>
<li>abcdef</li>
</ul>
</nav>
nav {
width: 100%;
line-height: 1.4em;
}
ul {
list-style: none;
display: lock;
width: 100%;
margin: 0;
padding: 0;
text-align: justify;
margin-bottom: -1.4em;
}
ul:after {
content: "";
display: inline-block;
width: 100%;
}
li {
display: inline-block;
}
Inheritance the a fundamental mechanism of CSS by which the computed values of some properties of an element are applied to its' children. This is particularly useful when you want to set a global style to your elements rather than having to set said properties to each and every element in your markup.
Common properties that are automatically inherited are: font, color, text-align, line-height.
#myContainer {
color: red;
padding: 5px;
}
This will apply color: red not only to the <div> element but also to the <h3> and <p> elements. However, due to the nature of padding its value will not be inherited to those elements.
<div id="myContainer"> <h3>Some header</h3> <p>Some paragraph</p> </div>
Some properties are not automatically inherited from an element down to its' children. This is because those properties are typically desired to be unique to the element (or selection of elements) to which the property is applied to. Common such properties are margin, padding, background, display, etc.
However, sometimes inheritance is desired anyway. To achieve this, we can apply the inherit value to the property that should be inherited. The inherit value can be appied to any CSS property and any HTML element.
#myContainer {
color: red;
padding: 5px;
}
#myContainer p {
padding: inherit;
}
This will apply color: red to both the <h3> and <p> elements due to the inheritance nature of the color property. However, the <p> element will also inherit the padding value from its' parent because this was specified.
<div id="myContainer"> <h3>Some header</h3> <p>Some paragraph</p> </div>
An image sprite is a single asset located within an image sprite sheet. An image sprite sheet is an image file that contains more than one asset that can be extracted from it.
The image above is an image sprite sheet, and each one of those stars is a sprite within the sprite sheet. These sprite sheets are useful because they improve performance by reducing the number of HTTP requests a browser might have to make.
So how do you implement one? Here's some example code.
<div class="icon icon1"></div> <div class="icon icon2"></div> <div class="icon icon3"></div>
.icon {
background: url("icons-sprite.png");
display: inline-block;
height: 20px;
width: 20px;
}
.icon1 {
background-position: 0px 0px;
}
.icon2 {
background-position: -20px 0px;
}
.icon3 {
background-position: -40px 0px;
}
By using setting the sprite's width and height and by using the background-position property in CSS (with an x and y value) you can easily extract sprites from a sprite sheet using CSS.
| Parameter | Details |
|---|---|
| clip-source | A URL which can point to an inline SVG element (or) an SVG element in an external file that contains the clip path's definition. |
| basic-shape | Refers to one among inset(), circle(), ellipse() or polygon. Using one of these functions the clipping path is defined. These shape functions work exactly the same way as they do in Shapes for Floats. |
| clip-geometry-box | This can have one among content-box, padding-box, border-box, margin-box, fill-box, stroke-box, view-box as values. When this is provided without any value for <basic-shape>, the edges of the corresponding box is used as the path for clipping. When used with a <basic-shape>, this acts as the reference box for the shape. |
| mask-reference | This can be none or an image or a reference URL to a mask image source. |
| repeat-style | This specifies how the mask should be repeated or tiled in the X and Y axes. The supported values are repeat-x, repeat-y, repeat, space, round, no-repeat. |
| mask-mode | Can be alpha or luminance or auto and indicates whether the mask should be treated as a alpha mask or a luminance mask. If no value is provided and the mask-reference is a direct image then it would be considered as alpha mask (or) if the mask-reference is a URL then it would be considered as luminance mask. |
| position | This specifies the position of each mask layer and is similar in behavior to the background-position property. The value can be provided in 1 value syntax (like top, 10%) or in 2 value syntx (like top right, 50% 50%). |
| geometry-box | This specifies the box to which the mask should be clipped (mask painting area) or the box which should be used as reference for the mask's origin (mask positioning area) dependingon the property. The list of possible values are content-box, padding-box, border-box, margin-box, fill-box, stroke-box, view-box. Detailed explanation of how each of those values work is available in the W3C Specs. |
| bg-size | This represents the size of each mask-image layer and has the same syntax as background-size. The value can be length or percentage or auto or cover or contain. Length, percentage and auto can either be provided as a single value or as one for each axis. |
| compositing-operator | This can be any one among add, subtract, exclude, multiply per layer and defines the type compositing operation that should be used for this layer with those below it. Detailed explanation about each value is available in the W3C Specs. |
With Clipping and Masking you can make some specified parts of elements transparent or opaque. Both can be applied to any HTML element.
Clips are vector paths. Outside of this path the element will be transparent, inside it's opaque. Therefore you can define a clip-path property on elements. Every graphical element that also exists in SVG you can use here as a function to define the path. Examples are circle(), polygon() or ellipse().
clip-path: circle(100px at center);
The element will be only visible inside of this circle, which is positioned at the center of the element and has a radius of 100px.
Masks are similar to Clips, but instead of defining a path you define a mask what layers over the element. You can imagine this mask as an image what consist of mainly two colors: black and white.
Luminance Mask: Black means the region is opaque, and white that it's transparent, but there is also a grey area which is semi-transparent, so you are able to make smooth transitions.
Alpha Mask: Only on the transparent areas of the mask the element will be opaque.
This image for example can be used as a luminance mask to make for an element a very smooth transition from right to left and from opaque to transparent.
The mask property let you specify the the mask type and an image to be used as layer.
mask: url(masks.svg#rectangle) luminance;
An element called rectangle defined in masks.svg will be used as an luminance mask on the element.
div {
height: 200px;
width: 200px;
background: url(http://lorempixel.com/200/200/nature/1);
mask-image: linear-gradient(to right, white, transparent);
}
<div></div>
In the above example there is an element with an image as its background. The mask that is applied on the image (using CSS) makes it look as though it is fading out from left to right.
The masking is achieved by using a linear-gradient that goes from white (on the left) to transparent (on the right) as the mask. As it is an alpha mask, image becomes transparent where the mask is transparent.
Note: As mentioned in remarks, the above example would work in Chrome, Safari and Opera only when used with the -webkit prefix. This example (with a linear-gradient as mask image) is not yet supported in Firefox.
div {
width: 200px;
height: 200px;
background: teal;
clip-path: circle(30% at 50% 50%); /* refer remarks before usage */
}
<div></div>
This example shows how to clip a div to a circle. The element is clipped into a circle whose radius is 30% based on the dimensions of the reference box with its center point at the center of the reference box. Here since no <clipgeometry-box> (in other words, reference box) is provided, the border-box of the element will be used as the reference box.
The circle shape needs to have a radius and a center with (x,y) coordinates:
circle(radius at x y)
div {
width: 200px;
height: 200px;
background: teal;
clip-path: polygon(0 0, 0 100%, 100% 50%); /* refer remarks before usage */
}
<div></div>
In the above example, a polygonal clipping path is used to clip the square (200 x 200) element into a triangle shape. The output shape is a triangle because the path starts at (that is, first coordinates are at) 0 0 - which is the top-left corner of the box, then goes to 0 100% - which is botom-left cornder of the box and then finally to 100% 50% which is nothing but the right-middle point of the box. These paths are self closing (that is, the starting point will be the ending point) and so the final shape is that of a triangle.
This can also be used on an element with an image or a gradient as background.
div {
width: 200px;
height: 200px;
background: url (http://lorempixel.com/ 200/200/abstract/6);
mask-image: radial-gradient (circle farthest-side at center, transparent 49%, white 50%); /* check remarks before using */
}
In the above example, a transparent circle is created at the center using radial-gradient and this is then used as a mask to produce the effect of a circle being cut out from the center of an image.
div { /* check remarks before usage */
height: 200px;
width: 400px;
background-image: url(http://lorempixel.com/400/200/nature/4);
mask-image: linear-gradient(to top right, transparent 49.5%, white 50.5%), linear-gradient(to top
left, transparent 49.5%, white 50.5%), linear-gradient(white, white);
mask-size: 75% 25%, 25% 25%, 100% 75%;
mask-position: bottom left, bottom right, top left;
mask-repeat: no-repeat;
}
<div></div>
In the above example, three linear-gradient images (which when placed in their appropriate positions would cover 100% x 100% of the container's size) are used as masks to produce a transparent triangular shaped cut at the bottom of the image.
| Value | Description |
|---|---|
| auto | Default. Automatic page breaks. |
| always | Always insert a page break. |
| avoid | Avoid page break (if possible). |
| left | Insert page breaks so that the next page is formatted as a left page. |
| right | Insert page breaks so that the next page is formatted as a right page. |
| initial | Sets this property to its default value. |
| inherit | Inherits this property from its parent element. |
@media print {
p {
page-break-inside: avoid;
}
h1 {
page-break-before: always;
}
h2 {
page-break-after: avoid;
}
}
This code does 3 things:
To add a background-image rule via the CSSOM, first get a reference to the rules of the first stylesheet:
var stylesheet = document.styleSheets[0].cssRules;
Then, get a reference to the end of the stylesheet:
var end = stylesheet.length − 1;
Finally, insert a background-image rule for the body element at the end of the stylesheet:
stylesheet.insertRule("body { background-image:
url('http://cdn.sstatic.net/Sites/stackoverflow/img/favicon.ico');}", end);
The browser identifies tokens from stylesheet and coverts them into nodes which are linked into a tree structure. The entire map of all the nodes with their associated styles of a page would be the CSS Object Model.
To display the webpage, a web browser takes following steps.
| Parameter | Details |
|---|---|
| (property: value) | Evaluates true if the browser can handle the CSS rule. The parenthesis around the rule are |
| required. | |
| and | Returns true only if both the previous and next conditions are true. |
| not | Negates the next condition. |
| or | Returns true if either the previous or next condition is true. |
| (...) | Groups conditions. |
@supports (display: flex) {
/* Flexbox is available, so use it */
.my-container {
display: flex;
}
}
In terms of syntax, @supports is very similar to @media, but instead of detecting screen size and orientation, @supports will detect whether the browser can handle a given CSS rule.
Rather than doing something like @supports (flex), notice that the rule is @supports (display: flex).
To detect multiple features at once, use the and operator.
@supports (transform: translateZ(1px)) and (transform-style: preserve-3d) and (perspective: 1px) {
/* Probably do some fancy 3d stuff here */
}
There is also an or opeartor and a not operator:
@supports (display: flex) or (display: table-cell) {
/* Will be used if the browser supports flexbox or display: table-cell */
}
@supports not (webkit-transform −: translate(0, 0, 0)) {
/* Will *not* be used if the browser supports -webkit-transform: translate(...) */
}
For the ultimate @supports experience, try grouping logical expressions with parenthesis:
@supports ((display: block) and (zoom: 1)) or ((display: flex) and (not(display: table-cell))) or
(transform: translateX (1px) ) {
/* ... */
}
This will work if the browser
In this example every positioned element creates its own stacking context, because of their positioning and z-index values. The hierarchy of stacking contexts is organized as follows:
It is important to note that DIV #4, DIV #5 and DIV #6 are children of DIV #3, so stacking of those elements is completely resolved within DIV#3. Once stacking and rendering within DIV #3 is completed, the whole DIV #3 element is passed for stacking in the root element with respect to its sibling's DIV.
<div id="div1">
<h1>Division Element #1</h1>
<code>position: relative;<br/>
z-index: 5;</code>
</div>
<div id="div2">
<h1>Division Element #2</h1>
<code>position: relative;<br/>
z-index: 2;</code>
</div>
<div id="div3">
<div id="div4">
<h1>Division Element #4</h1>
<code>position: relative;<br/>
z-index: 6;</code>
</div>
<h1>Division Element #3</h1>
<code>position: absolute;<br/>
z-index: 4;</code>
<div id="div5">
<h1>Division Element #5</h1>
<code>position: relative;<br/>
z-index: 1;</code>
</div>
<div id="div6">
<h1>Division Element #6</h1>
<code>position: absolute;<br/>
z-index: 3;</code>
</div>
</div>
* {
margin: 0;
}
html {
padding: 20px;
font: 12px/20px Arial, sans-serif;
}
div {
opacity: 0.7;
position: relative;
h1 {
font: inherit;
font-weight: bold;
}
#div1,
#div2 {
border: 1px dashed #696;
padding: 10px;
background-color: #cfc;
#div1 {
z-index: 5;
margin-bottom: 190px;
#div2 {
z-index: 2;
#div3 {
z-index: 4;
opacity: 1;
position: absolute;
top: 40px;
left: 180px;
width: 330px;
border: 1px dashed #900;
background-color: #fdd;
padding: 40px 20px 20px;
}
#div4,
#div5 {
border: 1px dashed #996;
background-color: #ffc;
}
#div4 {
z-index: 6;
margin-bottom: 15px;
padding: 25px 10px 5px;
}
#div5 {
z-index: 1;
margin-top: 15px;
padding: 5px 10px;
}
#div6 {
z-index: 3;
position: absolute;
top: 20px;
left: 180px;
width: 150px;
height: 125px;
border: 1px dashed #009;
padding-top: 125px;
background-color: #ddf;
text-align: center;
}
img {
float: left;
width: 100px;
margin: 0 10px;
}
.div1 {
background: #f1f1f1;
/* does not create block formatting context */
}
.div2 {
background: #f1f1f1;
overflow: hidden;
/* creates block formatting context */
}
Using the overflow property with a value different to visible (its default) will create a new block formatting] [context. This is technically necessary if a float intersected with the scrolling element it would forcibly rewrap the content.
This example that show how a number of paragraphs will interact with a floated image is similar to CSS Tricks example on CSS-tricks.com.
<div class="wrapper">
<div class="outer">
<div class="inner">
centered
</div>
</div>
</div>
.wrapper {
height: 600px;
text-align: center;
}
.outer {
display: table;
height: 100%;
width: 100%;
}
.outer .inner {
display: table-cell;
text-align: center;
vertical-align: middle;
}
<div class="container"> <div class="child"></div> </div>
.container {
height: 500px;
width: 500px;
display: flex; // Use Flexbox
align-items: center; // This centers children vertically in the parent
justify-content: center; // This centers children horizontally
background: white;
}
.child {
width: 100px;
height: 100px;
background: blue;
}
<div class="wrapper">
<div class="centered">
centered
</div>
</div>
.wrapper {
position: relative;
height: 600px;
}
.centered {
position: absolute;
z-index: 999;
transform: translate(-50%, -50%);
top: 50%;
left: 50%;
}
<div class="container"> <span>vertically centered</span> </div>
.container {
height: 50px; /* set height */
line-height: 50px; /* set line-height equal to the height */
vertical-align: middle; /* works without this rule, but it is good having it explicitly set */
}
Note: This method will only vertically center a single line of text. It will not center block elements correctly and if the text breaks onto a new line, you will have two very tall lines of text.
<div class="wrapper"> <img src="http://cdn.sstatic.net/Sites/stackoverflow/company/img/logos/so/so-icon.png?v=c78bd457575a"> </div>
.wrapper {
position: relative;
height: 600px;
}
.wrapper img {
position: absolute;
top: 0;
left: 0;
right: 0;
bottom: 0;
margin: auto;
}
If you want to center other then images, then you must give height and width to that element.
<div class="wrapper">
<div class="child">
make me center
</div>
</div>
<div class="wrapper"> <div class="content"> </div> </div>
.wrapper {
min-height: 600px;
}
.wrapper:before {
content:"";
display: inline-block;
height: 100%;
vertical-align: middle;
}
.content {
display: inline-block;
height: 80px;
vertical-align: middle;
}
This method is best used in cases where you have a varied-height .content centered inside .wrapper; and you want .wrapper's height to expand when .content's height exceed .wrapper's min-height.
The object-fit property will defines how an element will fit into a box with an established height and width. Usually applied to an image or video, Object-fit accepts the following five values:
object-fit: fill;
Fill stretches the image to fit the content box without regard to the image's original aspect ratio.
CONTAIN object-fit:contain;
Contain fits the image in the box's height or width while maintaining the image's aspect ratio.
COVER object-fit:cover;
Cover fills the entire box with the image. The image aspect ratio is preserved, but the image is cropped to the dimensions of the box.
None ignores the size of the box and is not resized.
object-fit:scale-down;
Scale-down either sizes the object as none or as contain. It displays whichever option results in a smaller image size.
These examples are for documenting CSS-specific design patterns like BEM, OOCSS and SMACSS.
These examples are NOT for documenting CSS frameworks like Bootstrap or Foundation.
BEM stands for Blocks, Elements, and Modifiers.
It's a methodology initially conceived by a Russian tech company
Yandex, But which gained quite some traction among American & Western-European
web developers as well.
As the name implies, BEM metholology is all about componentization of your HTML and CSS code into three types of components:
The goal of BEM is to optimize the readability, maintainability and flexibility of your CSS code. The way to achieve this, is to apply the following rules.
If you apply BEM to your form elements, your CSS selectors should look something like this:
.form { } // Block
.form−-theme-xmas { } // Block + modifier
.form−-simple { } // Block + modifier
.form__input { } // Block > element
.form__submit { } // Block > element
.form__submit−-disabled { } // Block > element + modifier
<form class="form form−-theme-xmas form−-simple"> <input class="form__input" type="text"/> <input class="form__submit form__submit−-disabled" type="submit"/> </form>
| Prefix } Browser(s) | |
|---|---|
| -webkit- | Google Chrome, Safari, newer versions of Opera 12 and up, |
| Android, Blackberry and UC browsers | |
| -moz- | Mozilla Firefox |
| -ms- | Internet Explorer, Edge |
| -o- | Opera until version 12 |
| , -xv- | |
| -khtml- | Konquerer |
div {
-webkit-transition: all 4s ease;
-moz-transition: all 4s ease;
-o-transition: all 4s ease;
transition: all 4s ease;
}
div {
-webkit-transform: rotate(45deg);
-moz-transform: rotate(45deg);
-ms-transform: rotate(45deg);
-o-transform: rotate(45deg);
transform: rotate(45deg);
}
Every browser has a default set of CSS styles that it uses for rendering elements. These default styles may not be consistent across browsers because: the language specifications are unclear so base styles are up for interpretation, browsers may not follow specifications that are given, or browsers may not have default styles for newer HTML elements. As a result, people may want to normalize default styles across as many browsers as possible.
Browsers have a default set of CSS styles they use for rendering elements. Some of these styles can even be customised using the browser's settings to change default font face and size definitions, for example. The styles contain the definition of which elements are supposed to be block-level or inline, among other things.
Because these default styles are given some leeway by the language specifications and because browsers may not follow the specs properly they can differ from browser to browser.
This is where normalize.css comes into play. It overrides the most common inconsistencies and fixes known bugs.
So, by including normalize.css in your project your design will look more alike and consistent across different browsers.
You may have heard of reset.css. What's the difference between the two?
While normalize.css provides consistency by setting different properties to unified defaults, reset.css achieves consistency by removing all basic styling that a browser may apply. While this might sound like a good idea at first, this actually means you have to write all rules yourself, which goes against having a solid standard.
CSS resets take separate approaches to browser defaults. Eric Meyer’s Reset CSS has been around for a while. His approach nullifies many of the browser elements that have been known to cause problems right off the back. The following is from his version (v2.0 | 20110126) CSS Reset.
html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup,
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
margin: 0;
padding: 0;
border: 0;
font-size: 100%;
font: inherit;
vertical-align: baseline;
}
Normalize CSS on the other and deals with many of these separately. The following is a sample from the version (v4.2.0) of the code.
/**
* 1. Change the default font family in all browsers (opinionated).
* 2. Correct the line height in all browsers.
* 3. Prevent adjustments of font size after orientation changes in IE and iOS.
*/
/* Document
========================================================================== */
html {
font-family: sans-serif; /* 1 */
line-height: 1.15 ; /* 2 */
-ms-text-size-adjust: 100%; /* 3 */
-webkit-text-size-adjust: 100%; /* 3 */
}
/* Sections
========================================================================== */
/**
* Remove the margin in all browsers (opinionated).
*/
body {
margin: 0;
}
/**
* Add the correct display in IE 9-.
*/
article,
aside,
footer,
header,
nav,
section {
display: block;
}
/**
* Correct the font size and margin on 'h1' elements within 'section' and
* 'article' contexts in Chrome, Firefox, and Safari.
*/
h1 {
font-size: 2 em;
margin: 0.67em 0;
}
display: inline-block;
The display property with the value of inline-block is not supported by Internet Explorer 6 and 7. A work-around for this is:
zoom: 1; *display: inline;
The zoom property triggers the hasLayout feature of elements, and it is available only in Internet Explorer (woopie). The *display makes sure that the invalid property executes only on the affected browsers. Other browsers will simply ignore the rule.
In Internet Explorer 10+ and Edge, Microsoft provides the -ms-high-contrast media selector to expose the "High Contrast" setting from the browser, which allows the programmer to adjust their site's styles accordingly.
The -ms-high-contrast selector has 3 states: active, black-on-white, and white-on-black. In IE10+ it also had a none state, but that is no longer supported in Edge going forward.
@media screen and (− ms-high-contrast: active), (−ms-high-contrast: black-on-white) {
.header {
background: #fff;
color: #000;
}
}
This will change the header background to white and the text color to black when high contrast mode is active and it is in black-on-white mode.
@media screen and (−ms-high-contrast: white-on-black){
.header {
background: #000;
color: #fff;
}
}
Similar to the first example, but this specifically selects the white-on-black state only, and inverts the header colors to a black background with white text.
Microsoft Documentation on -ms-high-contrast. Not worth your time to read.
To target Internet Explorer 6 and Internet Explorer 7, start your properties with *:
.hide-on-ie6-and-ie7 {
*display: none; // This line is processed only on IE6 and IE7
}
To target Internet Explorer 8, wrap your selectors inside: @media \0.
It’s microsoft, so it really isn’t worth spending more time learning.
So pathetic. The only good MS code was stolen from Universities, Digital Equipment Corporation, Linux, Unix, everywhere.
@media\\ 0 screen {
.hide-on-ie8 {
display: none;
}
}
Everything between @media \0 screen { } is processed only by I
Changing some CSS attribute will trigger the browser to synchronously calculate the style and layout, which is a bad thing when you need to animate at 60fps.
Animate with left and top trigger layout.
#box {
left: 0;
top: 0;
transition: left 0.5s, top 0.5s;
position: absolute;
width: 50px;
height: 50px;
background-color: gray;
}
#box.active {
left: 100px;
top: 100px;
}
Demo (jsFiddle) took 11.7ms for rendering 9.8ms for painting.
Animate with transform with the same animation.
#box {
left: 0;
top: 0;
position: absolute;
width: 50px;
height: 50px;
background-color: gray;
transition: transform 0.5s;
transform: translate3d(0, 0, 0);
}
#box.active {
transform: translate3d(100px, 100px, 0);
}
Demo (jsFiddle) same animation, took 1.3ms for rendering, 2.0ms for painting.