When configuring WSS v3 (2007) for a public facing web site there are a number of steps to take to insure anonymous users don't have access to areas they shouldn't - removing default lists, modifying application pages to hide pulic views, locking down mysites, etc. - but there is one page that is absolutely necessary for everyone to access: osssearchresults.aspx. This page presents the list of search results and is the de facto target location for WSS search controls.
By default, viewing this page requires a user to be authenticated to the server. This can create a problem when your site definition includes the basic search control as it will attempt to render all search results on this page. To remedy this situation, locate the following text at the top of the file (inside the < % @ Page ... /> declaration) and remove it:
This setting determines the inheritance of the page from the generic application page base class; however, it is not required for the page to function. Anonymous uers will be able to view the page without having to login and search results will continue to be security trimmed so users without proper permissions will be unable to view restricted items.