Ran into this little annoyance while flipping around in my Mozilla Firefox in Linux. Being used to Windows I keep hitting backspace to return the the previous webpage.. but in Mozilla Firefox for Linux it is not possible, by design I think, at least not by default.
This is more or less a rip from LinuxMint WiKi turorial on how to make Firefox faster on Linux Mint
Before making any changes, please make sure you have a good backup of your prefs.js file from your Mozilla Firefox profile.
This has happened to be more then once. For some reason it seems like from time to time a client figures that it can't fetch a add-on and then it seems to tell every other Firefox client to just uninstall it.. problem is when this is all your add-ons.