You already seem to be running a Firefox Aurora 19.0 build.<br /> It is usually better to have such a possibly unstable nightly build that is updated daily alongside of a regular Firefox release version (i.e. Firefox 17.01), so you can fall back to that version in case of problems. Do a custom install and install each version in its own program folder to use multiple Firefox versions. *http://kb.mozillazine.org/Installing_Firefox#Linux Create a new profile exclusively for each Firefox version.<br /> Create a desktop shortcut with -P "profile" appended to the target to launch each Firefox version with its own profile. See these mozillaZine KB articles for information: * http://kb.mozillazine.org/Testing_pre-release_versions * http://kb.mozillazine.org/Profile_Manager#Creating_a_new_profile * http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox * http://kb.mozillazine.org/Bypassing_the_Profile_Manager Use the -no-remote command line switch to open another Firefox instance with its own profile and to run different Firefox instances simultaneously. * http://kb.mozillazine.org/Opening_a_new_instance_of_Firefox_with_another_profile