These days, the vast majority of your users will have monitors capable of 1024x768 or better.
Here's a link to another thread where I've provided more info on max/min page widths and current trends.
Web site with...
Dynamic Drive has a ton of CSS menus you can use. They've provided a bunch of styles to choose from, so you should be able to find one that'll do what you need it to do.
Dynamic Drive CSS Library- Practical CSS codes and examples
(They've also got CSS layout templates)