It's odd that something so simple as a mouse over, could cause such problems across different browsers.

Ideally you should have tested you site one stage at a time on different browsers, namely mozilla, internet explorer, netscape and opera?

You may have to do a total rewrite, or if you're lucky it could be something simple. That's prolly not much help.

[edit] Having said that I've just tested your site using my version of Internet explorer and it works fine. [/edit]