I created 2 login pages of same domain.
I put the form name different for 2 forms
This is the cleanest solution I have found to keep Firefox from auto completing.
Add this code snip-it above your input of type password.
As far as I can tell Firefox is looking for an input of type Password, and filling in the password and then adding the username to the input of type text above it. Without a name or an id the inputs don't get added to the post, but this is still a hack.