I think Wayne Sanders is being a bit unfair to IRED in his criticism of your rating system.
Sites do change, sometimes for the worse.
Other Sites move address and don't bother to inform directories. Some Sites even close down leaving just a domain name and nothing more. These are annoying problems faced by all directory managers. The only way to keep tabs on them is to do very regular checks. Even some of the earlier TOP 10 Sites are no longer at the address given.