Note that with Ovids solution you *may* have to parse out and include some or all of the hidden fields in the form as well as adding the user/pass fields, otherwise the login may fail.

Additionally the login STATE may be maintained by hidden fields in subsequent pages (you need to parse them out and add them into subsequent post login requests) or a SESSION COOKIE which you need to accept, save and pass with each post login request.

They forgot to specify the type for the UserID input box

You don't have to, the practical default is text

If you think about the transaction there is no data passed from browser to server about the type of field so provided the browser will render it you have no issue in the real world.