Short: Where can I get a deb file (for amd64 Ubuntu 12.04) of Firefox, of a version between what I have (freakin' *11*) and what the repositories offer, which I think is 31?
Long: I was pretty up to date on Firefox, up to 29ish. Then synaptic offered me to upgrade to 31. The previous upgrades had generally done good things, like fixing memory leaks or improving performance or adding that useful "Profiler" command. So I upgraded to 31. Different look, slow, I didn't like it. Downgrade, please. The only other version was *11*. All the old bugs are back. Help?