Unfortunately this is becoming more and more frequent. We are back to 2000s I.E. only websites... :(

I'm afraid there are only some options:

1) Mozilla aggressively tries to be Chrome compatible. 2) Focus on Developer Tools in order to "motivate" Developers to use Firefox instead to develop their apps. 3) Somehow a miracle comes and they gain market share.

Actually i like the direction of Mozilla is taking now days where they are adding lots of interesting usability to Firefox. Like taking screenshots, share/send menu etc... But it seems this is not enough to get new users :(