Few comments:
1. You don't show what style is currently selected, and there's no option to know what it is (if you didn't switch them all several times to remember their look).
2. Changing font size on mouseover event is not a good thing. It causes page content to jump up and down, and this is not so pretty-looking style.
3. Question text (in answers area) are highlighted when you point mouse over them. What is it for? This is useless action that confuses a visitor.
Also, it's :hover settings in some styles uses such colors that it is impossible to read what is written there.
4. The sliding "top" arrow and question text highlighting doesn't work in Opera (the latter is for good by my opinion).