I tried to create an account, but my user name is already taken.

This message appears when you try to create a new user account, but the system already has a user account with that name.

Is it possible that you already created an account with that name? If so, use the "Request new password" link to reset your password.

If you've never created an account on this site, then somebody beat you to the punch: the user name you requested is already being used by somebody else. You will need to pick a different user name.