Address bar in Firefox automatically redirecting to google search

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http://askubuntu.com – Whenever I type something in my address bar (other than a url), firefox automatically uses google search to give me results for it. Where can I change this behaviour of firefox from? I'm using Ubuntu 12.04 Gnome classic. Edit: Changing the behaviour as in, making another search engine as the default one. Edit1: What I want is -> While typing in the address bar, it should use a search engine of my choice to search. However, I want the search engine text box (the text box to the right of the address bar) to use google itself if I type in something there. (HowTos)