CSS

===Declaration block===
A declaration block consists of a pair of braces (<code>{}</code>) enclosing a semicolon-separated list of ''declarations''.<ref>{{Cite web |title=CSS Syntax Module Level 3 |url=https://www.w3.org/TR/css-syntax-3/#syntax-description |url-status=live |archive-url=https://web.archive.org/web/20231001223513/https://www.w3.org/TR/css-syntax-3/ |archive-date=1 October 2023 |access-date=1 October 2023 |website=W3C}}</ref> 

====Declaration====
Each declaration itself consists of a ''property'', a colon (<code>:</code>), and a ''value''. Optional white-space may be around the declaration block, declarations, colons, and semi-colons for readability.<ref>{{cite web |url=https://www.w3.org/TR/CSS21/syndata.html#q10 |title=W3C CSS2.1 specification for rule sets, declaration blocks, and selectors |publisher=World Wide Web Consortium |date=7 June 2011 |access-date=2009-06-20 |archive-url=https://web.archive.org/web/20080328113605/https://www.w3.org/TR/CSS21/syndata.html#q10 |archive-date=28 March 2008 |url-status=live }}</ref>

====Properties====
Properties are specified in the CSS standard. Each property has a set of possible values. Some properties can affect any type of element, and others apply only to particular groups of elements.<ref>{{cite web |url=https://www.w3.org/TR/CSS2/propidx.html |title=Full property table |publisher=W3C |access-date=2014-05-30 |archive-url=https://web.archive.org/web/20140530163211/https://www.w3.org/TR/CSS2/propidx.html |archive-date=2014-05-30 |url-status=live }}</ref><ref>{{Cite web|title=Index of CSS properties|url=https://www.w3.org/Style/CSS/all-properties.en.html|access-date=2020-08-09|website=W3C }}</ref>

====Values====
Values may be keywords, such as "center" or "inherit", or numerical values, such as {{code|code=200px|2=css}} (200 pixels), {{code|code=50vw|2=css}} (50 percent of the viewport width) or {{mono|80%}} (80 percent of the parent element's width).

Color values can be specified with keywords (e.g. "{{code|code=red|2=css}}"), hexadecimal values (e.g. {{code|code=#FF0000|2=css}}, also abbreviated as {{code|code=#F00|2=css}}), RGB values on a 0 to 255 scale (e.g. <code>{{code|code=rgb(255, 0, 0)|2=css}}</code>), RGBA values that specify both color and alpha transparency (e.g. {{code|code=rgba(255, 0, 0, 0.8)|2=css}}), or HSL or HSLA values (e.g. {{code|code=hsl(0 100% 50%)|2=css}}, {{code|code=hsl(0 100% 50% / 0.8)|2=css}}).<ref>{{cite web |url=https://developer.mozilla.org/en-US/docs/Web/CSS/color |title=CSS Color |publisher=MDN Web Docs |date=2024-04-05 |access-date=2024-04-05 |archive-url=https://web.archive.org/web/20240327000753/https://developer.mozilla.org/en-US/docs/Web/CSS/color |archive-date=2024-03-27 |url-status=live }}</ref>

Non-zero numeric values representing linear measures must include a length unit, which is either an alphabetic code or abbreviation, as in <code>200px</code> or <code>50vw</code>; or a percentage sign, as in <code>80%</code>. Some units – <code>cm</code> ([[centimetre]]); <code>in</code> ([[inch]]); <code>mm</code> ([[millimetre]]); <code>pc</code> ([[Pica (typography)|pica]]); and <code>pt</code> ([[Point (typography)|point]]) – are ''absolute'', which means that the rendered dimension does not depend upon the structure of the page; others – <code>em</code> ([[Em (typography)|em]]); <code>ex</code> ([[Ex (typography)|ex]]) and <code>px</code> ([[pixel]]){{clarify|reason=This "such as" is carrying too much weight. The size of a px is relative not to the font size, but to screen resolution and viewing distance. Furthermore, in CSS 3 the "px" becomes the primordial absolute unit as the length units become anchored to it.|date=March 2022}} – are ''relative'', which means that factors such as the font size of a parent element can affect the rendered measurement. These eight units were a feature of CSS 1<ref>{{cite web |url=https://www.w3.org/TR/REC-CSS1-961217#length-units |title=6.1 Length units |work=Cascading Style Sheets, level 1 |date=17 December 1996 |access-date=20 June 2019 |archive-url=https://web.archive.org/web/20190614194847/https://www.w3.org/TR/REC-CSS1-961217#length-units |archive-date=14 June 2019 |url-status=live }}</ref> and retained in all subsequent revisions. The proposed CSS Values and Units Module Level 3 will, if adopted as a W3C Recommendation, provide seven further length units: <code>ch</code>; <code>Q</code>; <code>rem</code>; <code>vh</code>; <code>vmax</code>; <code>vmin</code>; and <code>vw</code>.<ref>{{cite web |url=https://www.w3.org/TR/2019/CR-css-values-3-20190606/#lengths |title=5. Distance Units: the &lt;length&gt; type |work=CSS Values and Units Module Level 3 |date=6 June 2019 |access-date=20 June 2019 |archive-url=https://web.archive.org/web/20190607171702/https://www.w3.org/TR/2019/CR-css-values-3-20190606/#lengths |archive-date=7 June 2019 |url-status=live }}</ref>