Use this CSS reference to browse an alphabetical index of all of the standard CSS properties, pseudo-classes, pseudo-elements, data types, functional notations and at-rules. You can also browse key CSS concepts and a list of selectors organized by type. Also included is a brief DOM-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 of selectors, pseudo-classes, and pseudo-elements below. The syntax for each specified value depends on the data type defined for each specified property.

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 our guide on CSS Selectors. Be aware that any syntax 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) is object-based.

At-rule syntax

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

Index

Selectors

The following are the various selectors, 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 selector elementname
• Class selector .classname
• ID selector #idname
• Attribute selector [attr=value]

Grouping selectors

Selector list A, B

Specifies that both A and B 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 of B" or "A is adjacent to B", creating a complex selector.

Next-sibling combinator A + B

Specifies that the elements selected by both A and B have the same parent and that the element selected by B immediately follows the element selected by A horizontally.

Subsequent-sibling combinator A ~ B

Specifies that the elements selected by both A and B share the same parent and that the element selected by A comes before—but not necessarily immediately before—the element selected by B.

Child combinator A > B

Specifies that the element selected by B is the direct child of the element selected by A.

Descendant combinator A B

Specifies that the element selected by B is a descendant of the element selected by A, but is not necessarily a direct child.

Column combinator A || B

Specifies that the element selected by B is located within the table column specified by A. 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)