Lol I was going to mention that but for some reason decided not too.
I think you can do it in IE too, but I've been using Firefox for so long I don't remember
I found a new handy program (free!) that cleans your computers junk files out quite nicely. Its called CCleaner. No, I didn't stutter, there are two Cs. Found it in Pc Gamer magazine ^-^ www.ccleaner.com then follow your nose.
Yeah, it forces me to remember passwords, which isn't TOO bad of a thing. Usually.
Okaay clean.... okay thats nice. Now lets watch some Youtube vids. Um.. Favorites. not signed in.. Username. password..... craaaap.
It's cause it cleans up and deletes all the cookies in your temp internet files folder and when it does that it's erasing all the information in the cookie for each site. :p