To access my frequent flier account online I have a 9-digit account number and a password.
For some reason, the Aeroplan Web designers have decided to get creative with the GUI for logging in. Rather than providing a single HTML <input> element, they've divided it up into three separate input elements.
The problem is, Firefox's password manager can only recognize one of the three input fields for form fill.
Consequently, only the last 3 get filled in automatically.
I guess the lesson is that if a request for identity isn't properly posed then the IDP can't respond.