I think you've just managed to confuse me even further, Henry ;-)
How did Lonely Planet come into this? (I've just checked out their web page and I can't see anything like you describe).
Forget Firefox for a while. Switch back to Internet Explorer. If everything's working fine with Internet Explorer, you need to reinstall Firefox. (You don't need to uninstall it first. Just install it on top of itself. All of your bookmarks and settings will be preserved).
If you can't view any websites in Internet Explorer, try typing this into the address bar:
72.14.205.147
(and, of course, click 'Go').
If doing that takes you to Google's home page (but typing in 'www' addresses doesn't), you need to sort out your DNS settings. (I can probably tell you how to do that but I'll wait until you've followed these instructions first).
Chris