I have a web site where some users authenticate with email/password and other users only require an email address to authenticate.
I'm trying to make the most natural login screen, but I'm struggling with the best way.
If I prompt for both email and password, users who come to the site without a password will be confused by the password box and perhaps assume they have a password they've forgotten.
If I don't have a textbox for a password, then I have to do a round trip to the server and then add a password prompt for those users that require it, making the login process for password-protected users a little clunky.
Does anyone have any links to sites that have solved this problem gracefully?