A Web site which checks the links on another site. Using such a commercial service is straightforward: all that has to be provided is the URL of a Web site. When this has been done the service provides periodic reports on the state of the site and identifies when one of its hyperlinks has been broken. The service offered by Internet service providers is becoming more and more sophisticated, with facilities including notification via pagers of any problems with a site. See also link checker, HTML validation site and Web rot.