Standard troubleshooting steps
firefox -safe-mode
Reset preferences ( Safe mode option )
Troubleshoot plugins Disable plugins ( Ex: Adobe Reader, Flash, Java, QuickTime, RealPlayer, and VLC )
firefox -ProfileManager
Slowness when browsing?
Many of these reference user.js [1] but you can use the about:config url as well if you prefer. Using user.js is preferable because Mozilla will not change these settings on your behalf, and you can easily undo them if something goes awry.
Go to your profile folder [2]and vacuum your db files
cd $HOME/.mozilla/firefox/*.default/; for i in *.sqlite; do echo "VACUUM;" | sqlite3 $i ; done
Disable favicon and site-icon caching. Append do your user.js file: [3] [4]
user_pref("browser.chrome.favicons", false); user_pref("browser.chrome.site_icons", false);
Turn off IPv6. Append to your user.js file: [5]
user_pref("network.dns.disableIPv6", true);
Disable dbus notifications within Firefox. Append to your user.js file: [6]
user_pref("toolkit.networkmanager.disable", true);
Turn off rich colour support. Append to user.js: [7]
user_pref("gfx.color_management.enabled", false); user_pref("gfx.color_management.mode", 0);
Enable form colours. Append to user.js: [8]
user_pref("browser.display.use_focus_colors", true); user_pref("browser.display.focus_text_color", "#010101");
Additional hidden prefs can be found here: [https://www.mozilla.org/unix/customizing.html ]