Wow, a lot of replies…
I have fixed the windows problem. (for exact, understood why the problem occured)
But cannot fix the problem with Safari.
I have uploaded a mov. / .ogv movie, but when I try on Safari, and click fullscreen. It widens from the spot it is placed. So, for example if I put the video on the middle of the screen, It widens from that spot. So fullscreen actually works when I put the video on the top-right side, since when I click fullscreen, it widens to the bottom-left.
So, to summarize it, fullscreen widens from the spot it is located. Widened by the same ratio with the screen, but the screen is sliced.