Recently I installed a freeware which came with ask.com plugin for firefox. This plugin after installing became default for lot of features in the browser which was really irritating me so had to remove the plugin.
Even then any search I do by entering the keyword directly in the address bar (location bar) went through ask.com. If you are also facing similar problem here are the steps to set your favorite search engine.
1. Type in about:config in the location bar and press Enter
2. You might see the This might void your warranty! warning screen. Click I’ll be careful, I promise! to continue.
3. Enter keyword.URL in search field and press Enter.
4. Double click the keyword.URL to modify the value. Here is the list of URL for different search engines.
To disable this feature enter keyword.enabled and double click to set the value to true.