Firefox 4 had recently changed its standard address bar to Omni bar which is actually a combination of both the address bar and a search bar, since it incorporates both of them into a single bar. Although the default search engine for Firefox 4 is the standard Google search, you can change it to whatever search engine you like, be it Yahoo, Bing or Ask using the tutorial given below:
Load Firefox browser. Type about:config in the Firefox 4 Address bar and hit enter.
You will come across a Filter field search. Right click on it and click on Modify.
A dialog box will open up asking you to enter a string value in the keyword.URL tab. Now you need to the url of the search engine you want to change the default search engine to. Here are the different urls you should enter for different search engines:
Yahoo : http://search.yahoo.com/search?p=
Bing : http://www.bing.com/search?q=
Ask : http://www.ask.com/web?q=
If you want to change it back to the default Google search engine, you can do so by typing http://www.google.com/search?ie=UTF-8&q=
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