At-rules - CSS: Cascading Style Sheets
at-rules are css statements that instructs css how to behave.
... /* general structure */ @identifier (rule); /* example: tells browser to use utf-8 character set */ @charset "utf-8"; there are several at-rules, designated by their identifiers, each with a different syntax: @charset — defines the character set used by the style sheet.
... nested at-rules — a subset of nested statements, which can be used as a statement of a style sheet as well as inside of conditional group rules: @media — a conditional group rule that will apply its content if the device meets the criteria of the condition defined using a media query.
...And 3 more matches

Index - Web APIs
403 cssconditionrule api, cssom, interface, reference an object implementing the cssconditionrule interface represents a single condition css at-rule, which consists of a condition and a statement block.
... 404 csscounterstylerule api, css counter styles, interface, reference the csscounterstylerule interface represents an @counter-style at-rule.
... 405 cssgroupingrule api, cssom, interface, reference an object implementing the cssgroupingrule interface represents any css at-rule that contains other rules nested within it.
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CSS3 - Archive of obsolete content
css namespaces module recommendation since september 29th, 2011 adds the support for the xml namespaces by defining the notion of css qualified name, using the ' | ' syntax and adding the @namespace css at-rule.
... adds: support for downloadable fonts via the css @font-face at-rule.
...it also extends the related css font-variant shorthand property and introduces the @font-feature-values at-rule.
...And 3 more matches

@charset - CSS: Cascading Style Sheets
the @charset css at-rule specifies the character encoding used in the style sheet.
... it must be the first element in the style sheet and not be preceded by any character; as it is not a nested statement, it cannot be used inside conditional group at-rules.
... if several @charset at-rules are defined, only the first one is used, and it cannot be used inside a style attribute on an html element or inside the <style> element where the character set of the html page is relevant.
...And 3 more matches

Introducing the CSS Cascade - CSS: Cascading Style Sheets
this means that at-rules containing entities other than declarations, such as a @font-face rule containing descriptors, don't participate in the cascade.
... in these cases, only the at-rule as a whole participates in the cascade: here, the @font-face identified by its font-family descriptor.
... while the declarations contained in most at-rules — such as those in @media, @document, or @supports — participate in the cascade, declarations contained in @keyframes don't.
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Syntax - CSS: Cascading Style Sheets
at-rules that start with an at sign, '@' (u+0040 commercial at), followed by an identifier and then continuing up to the end of the statement, that is up to the next semi-colon (;) outside of a block, or the end of the next block.
... each type of at-rules, defined by the identifier, may have its own internal syntax, and semantics of course.
... any statement which isn't a ruleset or an at-rule is invalid and ignored.
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Using CSS animations - CSS: Cascading Style Sheets
this does not configure the actual appearance of the animation, which is done using the @keyframes at-rule as described in defining the animation sequence using keyframes below.
... the sub-properties of the animation property are: animation-name specifies the name of the @keyframes at-rule describing the animation’s keyframes.
...this is done by establishing two or more keyframes using the @keyframes at-rule.
...And 2 more matches

@page - CSS: Cascading Style Sheets
the @page css at-rule is used to modify some css properties when printing a document.
... the @page at-rule can be accessed via the css object model interface csspagerule.
...meanwhile do not use them within a @page at-rule.
... working draft no change from css level 2 (revision 1), though more css at-rules can be used inside a @page.

@supports - CSS: Cascading Style Sheets
the @supports css at-rule lets you specify declarations that depend on a browser's support for one or more specific css features.
...the rule may be placed at the top level of your code or nested inside any other conditional group at-rule.
... syntax the @supports at-rule associates a block of statements with a supports condition.
...'='<attr-modifier> = i | s examples testing for the support of a given css property @supports (animation-name: test) { … /* css applied when animations are supported without a prefix */ @keyframes { /* other at-rules can be nested inside */ … } } testing for the support of a given css property or a prefixed version @supports ((perspective: 10px) or (-moz-perspective: 10px) or (-webkit-perspective: 10px) or (-ms-perspective: 10px) or (-o-perspective: 10px)) { … /* css applied when 3d transforms, prefixed or not, are supported */ } testing for the non-support of a specific css propert...

CSSStyleSheet.insertRule() - Web APIs
for at-rules, both an at-identifier and the rule content.
... if trying to insert an @import at-rule after a style rule, the method aborts with a hierarchyrequesterror.
... if rule is @namespace and the rule-list has more than just @import at-rules and/or @namespace at-rules, the method aborts with an invalidstateerror.

@font-feature-values - CSS: Cascading Style Sheets
the @font-feature-values css at-rule lets you use a common name in the font-variant-alternates property for features activated differently in opentype.
... the @font-feature-values at-rule may be used either at the top level of your css or inside any css conditional-group at-rule.
...ock>+where <feature-value-block> = <feature-type> '{' <feature-value-declaration-list> '}'where <feature-type> = @stylistic | @historical-forms | @styleset | @character-variant | @swash | @ornaments | @annotation<feature-value-declaration-list> = <feature-value-declaration>where <feature-value-declaration> = <custom-ident>: <integer>+; examples using @styleset in a @font-feature-values rule /* at-rule for "nice-style" in font one */ @font-feature-values font one { @styleset { nice-style: 12; } } /* at-rule for "nice-style" in font two */ @font-feature-values font two { @styleset { nice-style: 4; } } … /* apply the at-rules with a single declaration */ .nice-look { font-variant-alternates: styleset(nice-style); } specifications specification status comme...

@media - CSS: Cascading Style Sheets
the @media css at-rule can be used to apply part of a style sheet based on the result of one or more media queries.
... syntax the @media at-rule may be placed at the top level of your code or nested inside any other conditional group at-rule.
... /* at the top level of your code */ @media screen and (min-width: 900px) { article { padding: 1rem 3rem; } } /* nested within another conditional at-rule */ @supports (display: flex) { @media screen and (min-width: 900px) { article { display: flex; } } } for a discussion of media query syntax, please see using media queries.

CSS reference - CSS: Cascading Style Sheets
use this css reference to browse an alphabetical index of all of the standard css properties, pseudo-classes, pseudo-elements, data types, and at-rules.
... 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.
... concepts syntax and semantics css syntax at-rules cascade comments descriptor inheritance shorthand properties specificity value definition syntax css unit and value types 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-c...

Descriptor (CSS) - MDN Web Docs Glossary: Definitions of Web-related terms
a css descriptor defines the characteristics of an at-rule.
... at-rules may have one or multiple descriptors.

Index - MDN Web Docs Glossary: Definitions of Web-related terms
109 descriptor (css) css, codingscripting, glossary, needscontent a css descriptor defines the characteristics of an at-rule.
... at-rules may have one or multiple descriptors.