
Modify Location Bar autocomplete function
Option 1To prevent entries from History or bookmarked items from appearing but show those that you have specifically typed into the Location Bar (url bar).
1: Type about:config into your browser address bar and hit enter.
2: Then in the filter search bar type: browser.urlbar.matchonlytyped
3: Double click it so that it sets it to "true".
Option 2To completely disable the Location Bar autocomplete function in Firefox 3,
1: Type about:config into your browser address bar and hit enter.
2: Then in the filter search bar type: browser.urlbar.maxRichResults
3: Double click and set it to 0 (zero).
Ref: Mozilla support