1. Problem is, not everyone will know that they're supposed to hit Enter to submit, so you're already needlessly frustrating a percentage of your users (albeit, probably a small percentage) by hiding the submit button. Here's a bit more discussion on the topic, from a question I asked on UX StackExchange a while back: http://ux.stackexchange.com/questions/8876/usability-of-hidi...
Re:Login Screen – behind the scenes
by Stratoscope on Thursday October 11, 2012 @03:08PM
(#4642231)
Indeed. I've watched many friends fill in online forms, and I can't remember a single time any of them have ever used the Tab or Enter keys. They've all clicked on every field and finally on the Submit button.
2. What do people think about when you enter your email address and accidentally enter the wrong password: should the next page have whatever email address you initially entered re-displayed? Because the error message (rightfully) doesn't indicate whether the problem was actually with the password or whether you instead typo'ed the email address, would having this re-displayed allow the user to more easily recognize their mistake? (i.e., seeing that you typo'ed your email address is more helpful instead of first thought being that you've forgotten/mistaken your password)???