This tutorial shows you how to create a style switcher using jQuery and PHP. The end result will be an unobtrusive & entirely degradable dynamic style switcher which will be quick and easy to implement.

http://nettuts.com/javascript-ajax/jquery-style-switcher/
by James Padolsey

If the user has Javascript enabled, a very slick fade-in and fade-out affect is shown with a loading icon. If Javascript is disabled, the style-sheet switches and the same end result is seen.