User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:11.0) Gecko/20100101 Firefox/11.0 Build ID: 20120403131243 Steps to reproduce: On Ubuntu 12.04 with firefox 11.0 when you play fullscreen html5 youtube video and press Fn+F4 to make sound louder it will exit fullscreen. The same bug was happening some time ago with fullscreen flash, but it works ok now.

I've noticed the same issue. User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20100101 Firefox/13.0.1 Build ID: 20100924 Linux distro: Fedora 17 Steps to reproduce: Konstantine Rybnikov already already wrote that.

Same here (Firefox 15.0.1, Ubuntu Linux 12.04, x86-64): Adjusting volume with the keyboard's multimedia keys exits fullscreen mode. It doesn't just happen with youtube and volume, anything that enters fullscreen mode with html5 will exit if any multimedia keys are pressed (volume, play/pause, etc). Steps to reproduce: 1. Go to http://html5-demos.appspot.com/static/fullscreen.html 2. Enter fullscreen (either video or iframe, doesn't matter), accept 3. Press a multimedia key on your keyboard