FireFox Crashes

And I think it's due to whatever thing that the YouTube embedding Roph put in RMRK has:
http://rmrk.net/index.php/topic,38384.0.html is an example.

I'm facing this problem on multiple sites.

Firefox used to crash all of the time for me, and the sites it'd crash on would change with every FF update. There are huge threads of reports of firefox randomly crashing, and I don't doubt that mozilla tries to fix these bugs, but the crashes always seemed to happen.
You can try disabling all of your extensions and then enabling them one by one to see if it's any of them. That worked for a while for me.

I eventually got so fed up with it I stopped using it as my primary browser.

Yeah, it was my AVG link thing. Thanks :3 Awkwardly, the thing that screwed me up was the thing that was trying to protect me. P:

No problem! Glad I could help out.

The youtube embeds are just standard flash embeds. Try updating your flash player.