Firefox seems to have troubles displaying some web pages here. Especially long web pages.
You can see the troubles in the following video.
At the 26th second you can notice black bars displaying on far right and far left part of the screen, mixed with white bars, and at the end u can notice how the text overlaps and it's just weird, blackness, double text etc.
I have tried safe mode, clearing history, firefox on a virtual machine, firefox on my mom's labtop, same or very similar problems.
 I was at a friend's house, tried it, the problem doesnt exist there :O