Internet Address Bar/Window

Using Firefox, I have zero knowledge of any of the Internet Explorer family, but I would think you should set your Homepage to 'blank'.

In Firefox this would be done by accessing Tools > Options > Main tab.

If I understand correctly, you have a stored address you want to delete from pull down list. You can edit the registry key which contains the list:

To clear or the history of the address bar in IE only, without deleting your IE History folder, which contains history of links to pages that recently visited, follow these steps:

1. Close all Internet Explorer windows, then click on Start, then Run.
2. Run Registry Editor by typing RegEdit in the text box and click OK.
3. In Regedit, navigate to HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Typed URLs
4. Delete the registry key(s) (in the form of urlx, where x is 1, 2, 3,?.), which contains URL link that you doesn?t want to appear in address bar.

Note: If you delete only certain keys, make sure the remaining keys are in sequential order start from url1. Or else all keys will be corrupted and deleted. One way to avoid the problem is the select the URL that you want to keep in the IE address bar before performing above steps, so that the selected links will go on top, hence occupying lower sequence number.

Or use this utility:
http://www.aandrc.com/editurls/