first thing, make sure the chord from the monitor to the PC is tightly connected. Won't be the first time it was a little loose and then the screen messes up.   if that is good try another browser ... I want to see if it is the software or the video card on your PC ... if the same results most likely a going bad video card (assuming that things like digital photographs and other applications give you the same type of results ... if so a video card is very inexpensive to replace yourself.