Domain Helper currently works in cases where a URL includes a properly-spelled top-level domain (such as “.com”) at the end and where the site name is not a registered domain name. When activated, Domain Helper redirects users to a comcast.com page that is powered by Yahoo Bing search. The layout of the results, however, suggests that the goals are less about helping you find your intended destination and more about presenting you with ads.
Yet another reason to use OpenDNS.