The symptoms dont seem to point to needing to degauss as thats usually patchy areas of discolouration on the screen.
Dont worry if you havent got a degauss button as all TVs and Monitors have a degaussing circuit built in.
This degausses it on switching on,so if you think you have a problem just switching the monitor on and off will degauss it
As its not a web page fault,should this be moved to hardware