If you have intranet sites using Windows Auth that are not fully qualified domain names (fqdn) (like http://companyintranet/) you probably noticed that Firefox constantly prompts your users to enter their windows authentication credentials. You can easily get Firefox to work like IE by allowing automatic logins.
Go to “about:config”
Filter the keys down to “network.automatic”
Edit network.automatic-ntlm-auth.allow-non-fqdn value to true