You have one to many menu items in the main nav bar so is wrapping the menu and messing the template at the moment, In Firefox it's very bad, main body is not even on the screen. IE is showing the template intact but still wrapping the main nav.
Edit: I just read through this thread and noticed someone else noticed the same problem. I am a graphic artist and use all default settings in my browsers so as to have better idea what most people see. I also flush my cache often. I have just checked this site on 3 different PC's to be sure it's was not just mine.
Cheers