99% of the time, one of two things has happened:
1) Being an automated email, that confirmation email can sometimes be mistakenly filtered out as spam by your mail provider. Always check your spam/junk/bulk folder. Most of the time, it is in there.
2) You may have mistyped your email address. A single typo in your address during registration and that confirmation email is either on its way to a non-existent destination, or is dropping in on a very surprised individual with similar tastes in email handles as yourself.
You will find a "Resend Verification Email" link on the sign in page. Start by clicking it and trying to have it resent (being sure to check your spam/junk/bulk folder). If you don’t find it in your spam/junk/bulk folder, try signing up again, and be very careful how you type in that email address.