Firefox (Ver. 2.0) – Window Viewing Area

I have an annoying problem with Firefox: almost all site viewing area bleeds off screen (to the right).
Allowing a site to use scripts sometimes shifts the screen to viewable momentarily, but it always shifts back to a state of part of the right hand side unviewable.
I have some plug-ins installed.
When I must use IE to view a site, this does not happen.
All of my drivers are up to date and control panel settings appropriate.