The W3C has made it possible for a page’s entire design to be changed by switching the style sheet used. Although Internet Explorer doesn’t yet support this, both Mozilla-like browsers and Opera, do. Simply add a title and the words “alternate stylesheet” to the the link’s rel attribute:

<link rel="alternate stylesheet" title="New Style" type="text/css" media="screen" href="new.css">

Read “One page, many designs” for more details.