If I enter a fullscreen on a website(and firefox is in fullscreen mode), youtube for example, it goes in another Mac window, which is really weird for me. Because I want it to just stay on this window and be fullscreen also. How can I do it? But that's the only one part of a question, then if I exit a fullcreen youtube video, the window slides back to firefox with unwanted animation and gets unfullscreened, but then firefox also go to not fullscreen. Expected: 1) When I open video or something in a fullscreen, it should stay on firefox window, not create another one and slide in it. 2) When I switch back to normal mode on video, and not fullscreen and when it slides back to firefox window firefox should stay fullscreen. PS: I figured that it is only occurs with flash, when I use HTML5 features it is all cool. Still need to fix this coz there're only small part of sites use HTML5 System: Mac OS X 10.10/ firefox 38.0/Shockwave Flash 18.0 r0