Pseudo class :hover does not work in IE7

IE7 won't allow you to apply :hover pseudo-classes to non-anchor elements unless you explicitly specify a doctype. Just add a doctype declaration to your page and it should work perfectly.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
    "http://www.w3.org/TR/html4/strict.dtd">

More on IE7/quirks mode can be found on this blog post.