Even worse, when the password has an arbitrary length requirement of 20, but the site doesn't tell you and just cuts of any trailing characters exceeding the requirement during account creation.
You have no idea how long it took me to figure that one out.
Slightly easier to figure out but no less annoying is when the maxLength attributes on the password fields for the two forms (create account and login) are different.
You have no idea how long it took me to figure that one out.