You might check the "DPI" setting of Display Properties. Setting it to normal or a smaller size solved an "overprint" problem I had on some web pages with an older HP computer (a few years back). I don't recall whether my problem occurred on Internet Explorer (IE), Firefox, or both browsers.
Within Display Properties you should find the DPI setting at: Settings tab -> Advanced button -> General tab -> DPI settings of Display subsection.
To access "Display Properties", right click on blank area of desktop and then left click on "Properties" in the resulting context menu.
This solution (and others) is discussed by "TomdKat" toward the bottom of the following link:
Solved: Text Overwrite in Firefox . Yes, I know you're using Internet Explorer.