It is a well known fact that Google and Yahoo are the two leading search engines. Have you ever searched for something in Google or Yahoo, and was not satisfied from the results you got, so you had to run the same query on the other search site?
If you’re searching the web for information and you’re usually using Google, Yahoo or both of them you want to know this website: http://twingine.com/ .
From its name (Twingine) you can properly guess it what it does. Running a query on Twingine will result in two frames side by side. On one side you’ll see the results of your query on Yahoo, and on the other side you’ll see the result of the same query on Google. This way you are always searching on the two leading search engines and can pick the best result.