I want you to make a module:
* form validation
If there are some errors, it won't go to error page. Instead, back to form and show error messages just below fields that have errors. (Of course with every fields repopulated.)
* confirmation page
If there is no error, show confirmation page first so that user can check if the data just entered is correct or not, and go back and edit it needed.
* This module can use for registering new user too.