Oh dear. I unwittingly updated to Firefox/Iceweasel 29 in Debian testing. What a mistake! My Firefox setup has remained basically the same since the 3.5 days with a nice unobtrusive layout where I have the menu, navigation buttons, and the address bar in one strip and the tabs below. Despite hours of hair pulling there’s no way to get anything remotely satisfactory with the new UI, even with the “Classic Theme Restorer” addon.

Panic not! It’s possible to just stick with the stable 24.4 version from Debian wheezy! For future reference, this needs to go into /etc/apt/sources.list:

deb [arch=amd64] http://security.debian.org/ wheezy/updates main

Then do this:

sudo apt-get install -t wheezy iceweasel
sudo apt-mark hold iceweasel