By default, if you type in a phrase that is not a web address into the address bar, Firefox sends the query to Google for a web search. You can change this so that it uses a different search engine if you prefer.
For Windows Live search:
For a Yahoo search:
To go back to the default:
Change to any of the following above to use a different search engine.
You can also check out the Mozilla page for a complete list of configurations that you can change with descriptions at about:config wiki page. Any other about:config changes that you like? Post a comment!
[tags]about:config, firefox, about:config tweaks, firefox tweaks, firefox about:config[/tags]