Without seeing a screen shot or knowing which webpages and what happens it is not easy for me to answer. (Do you get the problem only on CNN ? are other pages ok ? )

Someone will give a better answer; and may well recognise what is happening from your system details; but meanwhile my suggestions

1. try View -> Page Style | [x] Basic Page Style
2. look at the Basic troubleshooting
3. if trying firefox safe mode do not make changes in the first dialogue window, just click the continue button

Clear the cache and the cookies from sites that cause problems.

• "Clear the Cache": Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"
• "Remove the Cookies" from sites causing problems: Tools > Options > Privacy > Cookies: "Show Cookies"

See also:

• http://kb.mozillazine.org/Website_colors_are_wrong
• http://kb.mozillazine.org/Websites_look_wrong