CSS (Cascading style sheets) is a style sheet language used to describe the presentation semantics( that is look and formating) of adocument written in markup language. Its most common application is to style web pages in HTML and XHTML, but the language can be applied to any kind of XML document, including SVG and XUL.
CSS is designed to enable the separation of document content (written in HTML or a similar markup language) from document presentation, including elements such as the colors fonts and layouts. This separation can improve
- Content accesability
- Provide more flexibility and control in the specification of presentation characteristics,
- Enable multiple pages to share formatting, and
- Reduce complexity and repetition in the structural content
CSS specifies a priority scheme to determine which style rules apply if more than one rule matches against a particular element.
- Separation of content from presentation
A style sheet will usually be stored in the browser cache, and can therefore be used on multiple pages without being reloaded, increasing download speeds and reducing data transfer over a network
- Page Reformatting
With a simple change of one line, a different style sheet can be used for the same page. This has advantages for accessibility, as well as providing the ability to tailor a page or site to different target devices