I think you're suffering from FF's and other's default css.
Look into YUI reset (
http://developer.yahoo.com/yui/reset/) for an exploration of x-browser css default(s) issues.
Add padding of 0 on: .menu ul. and see what happens
.menu ul {
list-style: none;
margin: 0;
padding: 0;
}
I noticed you're having an issue with a table down on the page a bit (issues' in all browsers).
It looks like the content's breaking the table out of its box. I assume you'll need to adjust the content.
I also noticed you have a selector of: float: center in your css. There is no float: center - only left, right, none and inherit.
That's just my quick look...