Click the menu button
, click help
and select Restart with Add-ons Disabled.... Firefox will start up with the Firefox Safe Mode dialog.
Note: You can also start Firefox in Safe Mode by holding down the shift key while starting Firefox.holding down the option key while starting Firefox.quitting Firefox and then going to your Terminal and running: firefox -safe-mode You may need to specify the Firefox installation path (e.g. /usr/lib/firefox)