I have been using the 64-bit build of FF18 on Debian amd64. It worked well, but manual upgrading is a pain and I got fed up of the constant nagging about updates. So I've tried to revert to the mainstream version. It apparently installed OK, and has successfully updated at least once, but gives avery appearance of having something missing. The chrome is so minimal that I can't see the edges of overlapping windows. The preferences dialogue looks completely skeletal. It may be that this is just a new style, but I have no way of telling whether it is, or whether it's just not installed correctly. I have tried installing alternate themes, but they just seem to tweak the banner image, it makes no real difference to the overall appearance. I can't get flash to work properly. Some examples seem to work OK, but about half of youtube brings up first a message saying I need a plugin, then a window claiming I don't have flash installed. If I revert to the FF18 that I've kept installed, flash works fine. I have tried several web guides that describe different methods of installing flash : all appear to work without errors but none improve the situation in firefox. Other players ask me to use a browser with native h.264 support. I have installed the codec packages from debian's repos with no effect. At present, it looks as though my best option is to fully revert to FF18 and turn off the nagging.