Change default Firefox Search engine to Bing, Wikipedia, Yahoo, etc.

Google is set as defult search engine and opens up when you hit enter after typing your query in address bar.

We usually search for any item in Firefox by two ways :
1) Search by typing the word in the Search Box.
2) Search by typing the word in the URL

Although the search box lets you allow searching , I find using the URL method more useful. But with advent of search engines like WoframAlpha , Bing , people do not want to  remain with Google Search and want to explore some new engines.

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- Source : http://blogsolute.com