Comment by seti0Cha

I'm not a heavy Firefox user, but I've seen it as well. I don't remember the specifics, but on a couple of occasions a site would fail to function properly, I'd pop the developer tools open and see a Javascript error, usually about a null object. I'm assuming some sites are relying on Chrome-specific extensions because they don't see enough Firefox traffic to care. I haven't really seen much in the way of broken layout though, which is a big difference from the old "only tested in IE" days.