Best thing you can do is hook the monitor up to another PC if available and see if you get the same issues. But this sounds more to do with your graphics card having artifacting issues.
If this is a desktop PC with an external monitor, make sure to try to swap out the monitor cable before you replace anything. A cheap, damaged, or failing monitor cable can cause all sorts of weird display issues.
If it is a laptop and if it has an external video port, try hooking it up to an external monitor to see if the problem carries over to an external display.
What browser, and have you tried disabling hardware acceleration?