I've accidentally sudo apt-get upgrade (while c/p-ing instructions to do something and failing to notice that it isn't sudo apt-get update) and it upgraded Firefox from 28 to 30. Now my menus are completely messed up, so I want FF28 back and I'm not interested in opinions how newer versions are better (there are plenty of those in Mozilla support forums instead of actual answers).

Also, downloading firefox-mozilla-build_28.0-0ubuntu1_i386.deb and trying to use it apparently doesn't work, Ubuntu software center says:

Breaks existing package 'firefox' that conflict: 'firefox'.