In my user signup form, I have a text field named twitter_username. After the form is submitted (for example, with the_real_shaq in the twitter username field), Firefox did this:
Do you want Firefox to remember the password for "the_real_shaq" on heroku.com?
Obviously I Firefox to offer to store the password for user's username on my site, not their supplied twitter username. How can I do this? Thanks for reading.