Firefox doesn't even start loading websites at random times. About half of the time it works well and loads pages and then it randomly stops loading again. I've tried all the steps here: https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can but the problem remains. As a coincidence I have a couple of friends with exactly the same problem - we all use Mac. (I wanted to add troubleshooting information but Firefox didn't work.)