[TheLML]

I've had problems when organizing online tournaments using Challonge. I've had to switch to Chrome a few times to do something, since it would regularly break in FF. Also their support page requires you to enter a combination of keys to reveal the email address: sadly this didn't work in FF, too. I've had a few other problems over time, but none that I remember off the top of my head. I've used FF for the past 15+ years and don't usually mind small problems, though.