Passmark is a concept/technology that is furhther discussed here. It works like this:
When a customer logs in to a bank's Web site, the bank shows the customer his PassMark -- a personalized image known only to the customer and the bank -- before asking for his password. Since a fake Web site will not know the customer's PassMark, it's safe for the customer to enter his password once he sees his PassMark. And PassMarks can also be used to authenticate outgoing email from the bank to the customer.
See also this analysis by Scot Loftesness.