I have this HTML code at the moment:
Theme Choose theme
Demo: http://jsfiddle.net/zYMFa/
Use values for options and handle change event for select. The value property of select gets value of the selected option, so you can use this.value in change function.
Default Theme 1 Theme 2 Theme 3 document.getElementById("myList").onchange = function() { setActiveStyleSheet(this.value); return false };