I'm on FF 49.0.2 under Windows 10 version 1607 and always have many tabs open - upto 30 - one of which is dedicated to YouTube channels, which I usually watch in fullscreen mode. I find that whatever the horizontal position of the 'YouTube' tab was before going into fullscreen, when I return to normal view the tab list has been re-positioned so that the YouTube tab is *always* pushed to the right side of the screen - up against the tab scroll right arrow. I believe that, on return from fullscreen, the tab should remain in its original horizontal position. Thanks