Hy, I've just instal firefox on my IMAC 27 Midd2011 on High Sierra after a re install of the system. Since I can't do anything. Firefox start after a long time and then nothing happen. Even if I click on a menu, nothing happens. I tried the different procedures with the help and reinstall it after reboot but nothing changes; I always have an "empty" window. If you have another idea, I am interested. Thank you so much