If you need Windows Authentication in firefox do the following:

Open firefox

Browse to about:config

Find “network.automatic-ntlm-auth.trused-uris”

Modify the value and enter in your intranet sites that you must pass your username and password to.

For some sites I connect to I also had to add values to:

“network.negotiate-auth.delegation-uris”
“network.negotiate-auth.trusted-uris”