I’m in the process of developing a website that uses the CSS Menu capability. The website, partially implemented, displays correctly in Safari and Camino and incorrectly in FireFox and Opera. Here is the URL
It looks like you’ve defined your page to be 1024 pixels wide and the table to be 1025. It may well be that some browsers are more tolerant of this than others.
If I’m reading the source wrong, well than I’ve just shown my ignorance in public. Oh well.