Use thisCSS reference to browse analphabetical index of all of the standardCSSproperties,pseudo-classes,pseudo-elements,data types,functional notations andat-rules. You can also browsekey CSS concepts and a list ofselectors organized by type. Also included is a briefDOM-CSS / CSSOM reference.

Basic rule syntax

Style rule syntax

style-rule ::=    selectors-list {      properties-list    }

Where:

selectors-list ::=    selector[:pseudo-class] [::pseudo-element]    [, selectors-list]properties-list ::=    [property : value] [; properties-list]

See the index ofselectors,pseudo-classes, andpseudo-elements below. The syntax for each specifiedvalue depends on the data type defined for each specifiedproperty.

Style rule examples

strong {  color: red;}div.menu-bar li:hover > ul {  display: block;}

For a beginner-level introduction to the syntax of selectors, see ourguide on CSS Selectors. Be aware that anysyntax error in a rule definition invalidates the entire rule. Invalid rules are ignored by the browser. Note that CSS rule definitions are entirely (Unicode)text-based, whereas DOM-CSS / CSSOM (the rule management system) isobject-based.

At-rule syntax

As the structure of at-rules varies widely, please seeAt-rule to find the syntax of the specific one you want.

Index

Selectors

The following are the variousselectors, which allow styles to be conditional based on various features of elements within the DOM.

Basic selectors

Basic selectors are fundamental selectors; these are the most basic selectors that are frequently combined to create other, more complex selectors.

• Universal selector*
• Type selectorelementname
• Class selector.classname
• ID selector#idname
• Attribute selector[attr=value]

Grouping selectors

Selector listA, B

Specifies that bothA andB elements are selected. This is a grouping method to select several matching elements.

Combinators

Combinators are selectors that establish a relationship between two or more simple selectors, such as "A is a child ofB" or "A is adjacent toB", creating a complex selector.

Next-sibling combinatorA + B

Specifies that the elements selected by bothA andB have the same parent and that the element selected byB immediately follows the element selected byA horizontally.

Subsequent-sibling combinatorA ~ B

Specifies that the elements selected by bothA andB share the same parent and that the element selected byA comes before—but not necessarily immediately before—the element selected byB.

Child combinatorA > B

Specifies that the element selected byB is the direct child of the element selected byA.

Descendant combinatorA B

Specifies that the element selected byB is a descendant of the element selected byA, but is not necessarily a direct child.

Column combinatorA || BExperimental

Specifies that the element selected byB is located within the table column specified byA. Elements which span multiple columns are considered to be a member of all of those columns.

Pseudo

Pseudo classes:

Specifies a special state of the selected element(s).

Pseudo elements::

Represents entities that are not included in HTML.

Concepts

Syntax and semantics

• CSS syntax
• At-rules
• Cascade
• Comments
• Descriptor
• Inheritance
• Shorthand properties
• Specificity
• Values
• Value definition syntax
• CSS values and units
• CSS functional notations

Values

• Actual value
• Computed value
• Initial value
• Resolved value
• Specified value
• Used value

Layout

• Block formatting context
• Box model
• Containing block
• Layout mode
• Margin collapsing
• Replaced elements
• Stacking context
• Visual formatting model

DOM-CSS / CSSOM

Major object types

• Document.styleSheets
• HTMLElement.style
• Element.className
• Element.classList
• StyleSheetList
• CSSRuleList
• CSSRule
• CSSStyleRule
• CSSStyleDeclaration

Important methods

• CSSStyleSheet.insertRule()
• CSSStyleSheet.deleteRule()

See also

• Mozilla CSS extensions (prefixed with-moz-)
• WebKit CSS extensions (mostly prefixed with-webkit-)

External Links

• CSS Indices (w3.org)