Something has changed with my Firefox browser where, it always launches in full screen. Then when I put it back to normal (F11), and go to watch a video on YouTube & click the little square in the corner of the video player to maximise the video to full screen, it always shows the top bar (URL box, tabs, and the little bit of grey underneath the URL bar). So basically I can't enjoy full screen videos on YouTube anymore. I really can't figure out why it's doing this. Please advise.