CSS reference

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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 ({{Glossary("ASCII")}} ) 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

[!NOTE] This index does not include SVG-exclusive presentation attributes, which can be used as CSS properties on SVG elements.

[!NOTE] The property names in this index do not include the JavaScript names which do differ from the CSS standard names.

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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 {{Experimental_Inline}} 
  • : 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.

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See also selectors in the Selectors specification and the pseudo-element specification.

Concepts

Syntax and semantics

• CSS syntax
• At-rules
• Cascade
• Comments
• Descriptor
• Inheritance
• Shorthand properties
• Specificity
• Value definition syntax
• CSS unit and value types
• 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

• {{DOMxRef("Document.styleSheets")}} 
• {{DOMxRef("HTMLElement.style")}} 
• {{DOMxRef("Element.className")}} 
• {{DOMxRef("Element.classList")}} 
• {{DOMxRef("StyleSheetList")}} 
• {{DOMxRef("CSSRuleList")}} 
• {{DOMxRef("CSSRule")}} 
• {{DOMxRef("CSSStyleRule")}} 
• {{DOMxRef("CSSStyleDeclaration")}} 

Important methods

• {{DOMxRef("CSSStyleSheet.insertRule()")}} 
• {{DOMxRef("CSSStyleSheet.deleteRule()")}} 

See also

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

External Links

• CSS Indices (w3.org)