1. In the Location bar, type about:config and press Enter.
The about:config "Here Be Dragons!" warning page may appear. Click I'll be careful, I promise!
2. In the filter box at the top, type keyword.
3. In the resulting grid, make sure the preference keyword.URL is set to the site you want to use. ie Google.com or .uk
To reset it to the default, right-clickhold down the Ctrl key while you click on the preference and select Reset.
4. Make sure that the preference keyword.enabled is set to true. If it is not, double-click on it to set it to true.