The title "Forget about this site" is misleading because it does not act like the "Forget about this site"-Button in Browser History. It does not delete the "site preferences". These include: Site-specific preferences, including the saved zoom level for sites, character encoding, and the permissions for sites (like pop-up blocker exceptions) described in the Page Info window.

It worked slick as everything for me, something I'd find extremely handy on sites like VentuSky or Google Maps that like to fill the history full but I don't have a toolbar button, and if I have to use a keyboard command I'll forget it's there.