If you haven't received your account activation email, the two most likely reasons are:
(1) Your email client has sent the email to your spam folder, or
(2) You gave us the wrong email address during account sign-up.
Here's a little troubleshooting guide to help you find the cause of the problem:
(1) Check your spam folder for an email with the subject "confirm your email address."
(2) If the email isn't in your spam folder, check to see if you entered the wrong email address by trying to create a new account with the email address you think you used before.
If you already used that address, the system will let you know that there's an existing account created using that address and won't create a new account for you. If this is the case, try waiting for a while and check your email again.
If it does let you create a new account, then you entered the wrong email before and you should now receive an activation email for the new account.
(3) If all the steps above fail, contact customer support.