Some websites I visit their pages go off the screen (not every website that is)...
Some website?
Is that very many or just a few?
Although apart from as has already been suggested, I don't think there may be much you can do about it.
If it's on forums, then it may be that someone has posted a "large" picture.
Although, I was on a Spanish site last night and the left-hand side of the page (the normal side) apart from the header was practically empty and all of the information was way of screen over to the right-hand side which was very annoying, probably the same as you are experiencing.
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edit.
I just tried my troublesome site again with IE and it now seems ok, I was previously using FF.
So unless they fixed their site, I don't know what the solution may be.
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edit
I just tried my troublesome site again this time with FF
Although on a different PC I still have the same problem as you (as I did before) so I suspect it could well be a setting in FF.
Viewing with IE does not give me the problem.
With FF, If you select the "RENTALS" link from their menu you will see what I mean.
http://www.propertyrentals.com/index.html"Although I appreciate this does not help or resolve your problem" sorry