I\'m not sure whether this bug applies to Firefox only or also to WebKit-based browsers, but it\'s really, really annoying.
I\'ve got a template/framework for my CMS in
First, be careful when pointing to somebody else's thing as the cause of your problems. Think to yourself which is more likely, that the issue is with the piece of code used by 200k users and 20k developers on a daily basis, or that it's in the thing used by you, for 4 hours now.
That said, your next step should be to reduce this down to a simple test page that contains just enough HTML to demonstrate the behavior. In your case, that would be a page like this:
This should cause scrollbars to show
One of two things will happen:
Either the problem won't appear, in which case you get to slowly add back the other things on your real-life page until you find out what was actually causing the issue.
Or the problem will still be there, in which case you can report back to us here. You will also then be able to file a bug report with the Mozilla folks.
Good luck!