When Firefox 4 opens it has margins at the top and right side of the screen that were not there before. When I double click the margin at the top it goes to the bottom. This is the case whether it is in full or regular screen modes. Also in regular mode the the buttons for minimize, maximize and exit are missing from the upper right corner but reappear in full screen mode. Then there is the problem of there being no margins but I can't access anything at the top of the screen. It will not pull down. I have to close F4 and hope the next session works. Sometimes that does not work and I have had to do a restart to get it to work again.