​If you are using Firefox as your default browser, then either you get
an IE tab add-on to view SharePoint sites in Firefox, or type your user
name and password each time when you access to the SharePoint server.

There is a way thought to allow you to save your typed Windows
credentials in Firefox to prevent you from repeatly typing the Windows
user name and password.

1. Enter “about:config” in the address bar of Firefox and hit [Enter]
2. Do a search on "ntlm", at least three entries should appear
3. Double click the entry titled
   "network.automatic-ntlm-auth.trusted-uris" and set its value to .yourdomain (do not
   forget the dot). You can have multiple domains by entering them as comma-separated.
4. Restart your Firefox to get it to kick in.

Woila! No more irritating login prompts. This only works with NTLM authentication and not Kerberos.