This is probably old news but I thought I’d share anyway. To get a single sign on experience (no authentication prompt for domain joined machines) do the following.

Open Firefox and goto:

about:config

Search for:

network.automatic-ntlm-auth.trusted-uris

Add:

domain.com

or

subdomain.domain.com

Note: domain.com has an implied wildcard so any subdomain will be included. Multiple domains can also be added if they are seperated by commas.