I might be missing something really simple and huge, or probably the question has been already asked, but I was not able to find it.
It has been some time now that my Firefox is not able to display correctly any GitHub page, not even its home page. It looks to me as if the CSS is not considered at all.
Everything looks ok on IE and Chrome. Here's a sample screenshot:
I'm on Windows 7 64bit, Firefox v8.0 (but it happened on previous versions too).
PS I was only able to find this unanswered question on google groups.