Sounds like you've got Windows authentication (NT Challenge/Response) turned on in IIS. Currently, IE is the only browser that supports this method of authentication. From: Christian Heilmann codepo8 at gmail.com > Can someone remind me how to set up the permissions to allow Firefox (and > others) to access my localhost? IE is working fine. It is not the hosts > file, as 127.0.0.1 localhost, already exists there. > This is for WinXP Professional.