The 'Exclude Referrer' box allows you to exclude from the stats all visits coming from a given referrer.
Simply enter a string contained in the referrer in question in the box. If a visitor comes to your site and his referrer matches the string you entered, the visit will not be counted. For instance to exclude all visits referred by google.com enter 'google.com'. If you want to eliminate all visits referred by google.com, google.ca, google.fr, google.co.uk, etc, enter 'google'