You have a corrupted User Agent, which is probably why the websites are telling you to update. Follow the Steps listed at http://support.mozilla.org/en-US/kb/websites-say-firefox-outdated-or-incompatible. After doing that, ensure that you are fully updated. Update Firefox to the latest release

Thanks Tyler but I give up. I'll wait until my nephew, who knows about computers, comes by this weekend. I tried going into about:config but it just didn't work. Thanks anyway.

Can you post the content of the Help > Troubleshooting Information page (preferences section)?

• https://support.mozilla.org/kb/Using+the+Troubleshooting+Information+page

You can use the search bar at the top of the about:config page to find the general.useragent.override pref as this one is the most likely candidate and reset this pref and maybe other user set (bold) general.useragent prefs to the default via the right-click context menu (Reset).

• http://kb.mozillazine.org/about:config