This website will test for common internet problems..
When searching Google, is your pages being redirected to something different? Are you getting random popups?
There is a quite well hidden virus that will redirect web pages whether your using Internet Explorer or Firefox. It also stops Chrome from loading any pages, and breaks Safari too.
It does this by hooking in to the system's DNS. Its not via the hosts file, and it works whether the DNS client service is running or not.
This virus will also stop specific pages from loading. Try to view update.microsoft.com will result in a 404 page.
The virus is hiding in the generic IDE driver 'atapi.sys', which is in c:\windos\system32\drivers\
Uninstalling, deleting, replacing the file will not work!
Get a clean copy of the atapi.sys. if you search your system for other copies you might be lucking. Note that the file size between infected and clean are no different. The best way to tell the difference is the modified date on the file. An infected one will have today's date on it.
I would be careful not to try installing the wrong one, as you could potentially completely stop your system from working, since this file controls all access to your files.
I would make a copy of the infected version, just incase you need to put it back just to get your system working again, (if that was possible anyhow.)
Once you have a clean copy. Look at the properties, and change it to 'readonly', then copy the file directly over the infected file.
Web pages should now be working fine.