Loss of Web Formatting in Firefox

Yesterday I had some SPAMware infect my computer, so I ran a slew of Norton diagnostics and utilities (including Norton Power Eraser).  I'm not sure if that had anything to do with my problem, but now I have lost the ability to view web pages in their regular format using Firefox 17.0.1 (I'm running the Windows 7 OS).  I tested the problem with Internet Explorer, and the problem doesn't exist, so it appears to be unique to Firefox.  IE makes me nervous, so I would like to keep using Firefox if I can get the problem resolved.  Attached are a couple of screen shots showing the problem.  

Thanks,

Phil