When you type a bad URL, you are supposed to get a "domain not found" error. Some ISPs have started trying to make money by instead taking you to a search page; the ISP gets a small amount of money each time someone does a search.
You have no control over this; there's no way you can control what your ISP does when you type a bad domain. The only thing you can do is set your computer to use a different ISP's domain name servers, and you'll get whatever those domain name servers when you type a bad URL.
If you have set the OpenDNS name servers in your network settings, you'll get the OpenDNS search page if you type a bad URL.
Google also has domain name servers of their own, but as of right now if you use their domain name servers and type a bad URL you just get an error message.
