cascading style sheets
Websites built using cascading style sheets load faster because page markup is leaner, as design elements have been separated from content and the file only needs to be downloaded once as it applies to all pages. Apart from fast loading, it also aids accessibility as text readers do not have to trawl through a maze of unnecessary markup, and search engines find it easier to index websites that use style sheets.
One of the major considerations when building a new website is to make it as accessible as possible. Not everyone can read text on a white background, text with a normal font weight or standard size. Alternatives should be available, and this is where CSS comes into its own. By providing a list of alternate style sheets called up by client or server-side scripts, a site user can determine how they view a website's content. This makes good business sense and shows consideration for those with visual or other impairments.
Costly website makeovers can also be avoided by the use of style sheets, as the altering of a single file is all that is needed to give your website a refreshing new look.