I wonder why you can't get to search engines? Can you get to other URLs?

I've no idea. I can get to any site if I type it into the address bar, but if I try Google I get a page saying the site's not there. I can get to Yahoo's main page but if I try the search function I get a page not found. After trying loads of search engines I finally got Dog Pile to work. It's okay but it's no Google :(

I thought it might be something to do with the security levels but I tweaked them for ages and nothing doing.