I have seen rather complex code out there for style sheet swapping in web browsers through JavaScript, and just found out a much simpler way works.
I could have sworn I tried to do real-time style sheet swapping a very long while back and none of my tests turned out satisfactorily, but a friend was just asking me about it, and I was redoing the tests, and it all worked out perfectly in an incredibly easy fashion in IE 6 & 7 and Firefox 2.5 & 3. All that needs to be done is swap the href of the link object pointing to the external style sheet file.
Adding style sheets by dynamically inserting HTML via JavaScript seemed to work just fine too.