Why do sites ask you to confirm your email address when registering? It makes no sense to me and is an annoying extra step in the registration process.
If I make a typo when entering my email address initially, I am more than likely going to copy and paste the mistake into the confirm field thereby negating any benefits of having this confirmation step.
If the site wants to be sure you are entering your email address correctly, then ensure that the setup involves emailing the account details. No details received? Then you check what email details you entered.
Make signups as painless as possible for potential users – it is criminal to lose people at this point in the proceedings.