Changing autocomplete behavior - Firefox
From MozillaZine Knowledge Base
The Location Bar, the Search Bar and some form fields on web pages have autocomplete dropdowns that appear with a list of previously entered data. To remove them, you will need to edit your config files.
Note that this is not a clean solution. It will cause some errors appear in the JavaScript Console if you have chrome errors enabled and may cause the browser to malfunction.
In userChrome.css, add the following lines:
/* Remove autocomplete dropdown */ #PopupAutoComplete > .autocomplete-tree { display: none !important; }
If you also want to remove the dropdown button at the far right of the Location Bar, add the following line:
.autocomplete-history-dropmarker { display: none !important; }
You may also want to enable inline autocomplete.