I accidentally dropped firefox from full-screen to half-screen and set it to fullscreen again, but when i open firefox, it... well, it does not look very ok...

well, when i click on the upper bar, it looks like that:

here it seems that firefox is drawn too far left, when i enter an url, it does not show until it is long enough... after another click in the bar, it is really full-screen...

how can i get rid of this problem?