Revision 941611 of CSS

<p>&lt;p&gt;&lt;span class="seoSummary"&gt;&lt;strong&gt;Cascading Style Sheets&lt;/strong&gt;, most of the time abbreviated as &lt;strong&gt;CSS&lt;/strong&gt;, is a &lt;a href="/en-US/docs/DOM/stylesheet"&gt;stylesheet&lt;/a&gt; language used to describe the presentation of a document written in &lt;a href="/en-US/docs/HTML" title="The HyperText Mark-up Language"&gt;HTML&lt;/a&gt;&lt;/span&gt; or &lt;a href="/en-US/docs/XML" title="en-US/docs/XML"&gt;XML&lt;/a&gt; (including various XML languages like &lt;a href="/en-US/docs/SVG" title="en-US/docs/SVG"&gt;SVG&lt;/a&gt; or &lt;a href="/en-US/docs/XHTML" title="en-US/docs/XHTML"&gt;XHTML&lt;/a&gt;). CSS describes how the structured element must be rendered on screen, on paper, in speech, or on other media.&lt;/p&gt;</p>

<p>&lt;p&gt;&lt;strong&gt;CSS&lt;/strong&gt; is one of the core languages of the &lt;em&gt;open web&lt;/em&gt; and has a standardized &lt;a class="external" href="https://w3.org/Style/CSS/#specs"&gt;W3C specification&lt;/a&gt;. Developed in levels, CSS1 is now obsolete, CSS2.1 is a recommendation, and &lt;a href="/en-US/docs/CSS/CSS3" title="CSS3"&gt;CSS3&lt;/a&gt;, now split into smaller modules, is progressing on the standardization track.&lt;/p&gt;</p>

<p>&lt;section id="sect1"&gt;<br />
 &lt;ul class="card-grid"&gt;<br />
 &nbsp;&lt;li&gt;&lt;span&gt;CSS Reference&lt;/span&gt;</p>

<p>&nbsp; &lt;p&gt;An &lt;a href="/en-US/docs/Web/CSS/Reference" title="en-US/docs/CSS/CSS_Reference"&gt;exhaustive reference&lt;/a&gt; for seasoned Web developers describing every property and concept of CSS.&lt;/p&gt;<br />
 &nbsp;&lt;/li&gt;<br />
 &nbsp;&lt;li&gt;&lt;span&gt;CSS Tutorial&lt;/span&gt;<br />
 &nbsp; &lt;p&gt;A &lt;a href="/en-US/docs/CSS/Getting_Started" title="en-US/docs/CSS/Getting_Started"&gt;step-by-step introduction&lt;/a&gt; to help complete beginners get started. It presents all the needed fundamentals.&lt;/p&gt;<br />
 &nbsp;&lt;/li&gt;<br />
 &nbsp;&lt;li&gt;&lt;span&gt;CSS3 Demos&lt;/span&gt;<br />
 &nbsp; &lt;p&gt;A &lt;a href="/en-US/demos/tag/tech:css3" title="https://developer.mozilla.org/en-US/demos/tag/tech:css3"&gt;collection of demos&lt;/a&gt; showing the latest CSS technologies in action: a boost for the creativity.&lt;/p&gt;<br />
 &nbsp;&lt;/li&gt;<br />
 &lt;/ul&gt;</p>

<p>&lt;div class="row topicpage-table"&gt;<br />
 &lt;div class="section"&gt;<br />
 &lt;h2 class="Documentation" id="Documentation" name="Documentation"&gt;Documentation and tutorials&lt;/h2&gt;</p>

<p>&lt;dl&gt;<br />
 &nbsp;&lt;dt&gt;CSS key concepts&lt;/dt&gt;<br />
 &nbsp;&lt;dd&gt;Describes the &lt;a href="/en-US/docs/CSS/Syntax" title="/en-US/docs/CSS/Syntax"&gt;syntax and forms of the language&lt;/a&gt; and introduces fundamentals like &lt;a href="/en-US/docs/CSS/Specificity" title="Specificity"&gt;specificity&lt;/a&gt; and &lt;a href="/en-US/docs/CSS/inheritance" title="inheritance"&gt;inheritance&lt;/a&gt;, the &lt;a href="/en-US/docs/CSS/box_model" title="Box model"&gt;box model&lt;/a&gt; and &lt;a href="/en-US/docs/CSS/margin_collapsing" title="Margin collapsing"&gt;margin collapsing&lt;/a&gt;, &lt;a href="/en-US/docs/CSS/Understanding_z-index/The_stacking_context" title="The stacking context"&gt;stacking&lt;/a&gt; and &lt;a href="/en-US/docs/CSS/block_formatting_context" title="block formatting context"&gt;block-formatting&lt;/a&gt; contexts, or the &lt;a href="/en-US/docs/CSS/initial_value" title="initial value"&gt;initial&lt;/a&gt;, &lt;a href="/en-US/docs/CSS/computed_value" title="computed value"&gt;computed&lt;/a&gt;, &lt;a href="/en-US/docs/CSS/used_value" title="used value"&gt;used&lt;/a&gt; and &lt;a href="/en-US/docs/CSS/actual_value" title="actual value"&gt;actual&lt;/a&gt; values. Entities like &lt;a href="/en-US/docs/CSS/Shorthand_properties" title="CSS/Shorthand_properties"&gt;CSS shorthand properties&lt;/a&gt; are also defined.&lt;/dd&gt;<br />
 &nbsp;&lt;dt&gt;&lt;a href="/en-US/docs/Web/Guide/CSS" title="/en-US/docs/Web/Guide/CSS"&gt;CSS developer guide&lt;/a&gt;&lt;/dt&gt;<br />
 &nbsp;&lt;dd&gt;Articles to help you learn everything from the basics of styling HTML with CSS to assorted &lt;strong&gt;CSS&lt;/strong&gt; techniques to make your content shine.&lt;/dd&gt;<br />
 &nbsp;&lt;dt&gt;&lt;a href="/en-US/docs/Web/CSS/Common_CSS_Questions"&gt;Common CSS questions&lt;/a&gt;&lt;/dt&gt;<br />
 &nbsp;&lt;dd&gt;Answers to common questions about &lt;strong&gt;CSS&lt;/strong&gt;.&lt;/dd&gt;<br />
 &lt;/dl&gt;<br />
 &lt;/div&gt;</p>

<p>&lt;div class="section"&gt;<br />
 &lt;h2 class="Tools" id="Tools" name="Tools"&gt;Tools for CSS development&lt;/h2&gt;</p>

<p>&lt;ul&gt;<br />
 &nbsp;&lt;li&gt;The &lt;a class="external" href="https://jigsaw.w3.org/css-validator/"&gt;W3C CSS Validation Service&lt;/a&gt; checks if a given CSS is valid. The service at &lt;a href="//www.OnlineWebCheck.com/"&gt;OnlineWebCheck.com&lt;/a&gt; also does the same. These are invaluable debugging tools.&lt;/li&gt;<br />
 &nbsp;&lt;li&gt;&lt;a href="/en-US/docs/Tools"&gt;Firefox Developer Tools&lt;/a&gt; allow viewing and editing live CSS of a page via the &lt;a href="/en-US/docs/Tools/Page_Inspector"&gt;Inspector&lt;/a&gt; and &lt;a href="/en-US/docs/Tools/Style_Editor"&gt;Style Editor&lt;/a&gt; tools.&lt;/li&gt;<br />
 &nbsp;&lt;li&gt;&lt;a class="link-https" href="https://addons.mozilla.org/en-US/firefox/addon/1843"&gt;Firebug extension&lt;/a&gt; for Firefox, a popular extension of that navigator that allows to edit live CSS on watched sites. Very practical to test some changes, though this extension does much more.&lt;/li&gt;<br />
 &nbsp;&lt;li&gt;&lt;a class="link-https" href="https://addons.mozilla.org/en-US/firefox/addon/60"&gt;Web Developer extension&lt;/a&gt; for Firefox also allows to watch and edit live CSS on watched sites. Simpler than Firebug, though less powerful.&lt;/li&gt;<br />
 &nbsp;&lt;li&gt;&lt;a href="/en-US/docs/Web/CSS/Tools"&gt;CSS tools&lt;/a&gt;.&lt;/li&gt;<br />
 &lt;/ul&gt;<br />
 &lt;/div&gt;<br />
 &lt;/div&gt;<br />
 &lt;/section&gt;</p>

<p>&lt;h2 id="See_also"&gt;See also&lt;/h2&gt;</p>

<p>&lt;ul&gt;<br />
 &nbsp;&lt;li&gt;Mozilla's &lt;a href="/en-US/Learn/CSS"&gt;Learning CSS section&lt;/a&gt;&lt;/li&gt;<br />
 &nbsp;&lt;li&gt;Web languages CSS is often applied to: &lt;a href="/en-US/docs/HTML" title="en-US/docs/HTML"&gt;HTML&lt;/a&gt;, &lt;a href="/en-US/docs/SVG" title="SVG"&gt;SVG&lt;/a&gt;, &lt;a href="/en-US/docs/XHTML" title="en-US/docs/XHTML"&gt;XHTML&lt;/a&gt; and &lt;a href="/en-US/docs/XML" title="en-US/docs/XML"&gt;XML&lt;/a&gt;.&lt;/li&gt;<br />
 &nbsp;&lt;li&gt;Mozilla technologies which make extensive use of CSS: &lt;a href="/en-US/docs/Mozilla/Tech/XUL" title="en-US/docs/XUL"&gt;XUL&lt;/a&gt;, &lt;a href="/en-US/Firefox"&gt;Firefox&lt;/a&gt;, and &lt;a href="/en-US/docs/Mozilla/Thunderbird"&gt;Thunderbird&lt;/a&gt; &lt;a href="/en-US/docs/Extensions" title="en-US/docs/Extensions"&gt;extensions&lt;/a&gt; and &lt;a href="/en-US/Add-ons/Themes" title="en-US/docs/Themes"&gt;themes&lt;/a&gt;.&lt;/li&gt;<br />
 &lt;/ul&gt;</p>

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