Anonymous user not specified for site &1.
&2 - The unique identification of the Site.
For each site, an anonymous user must be specified. This user provides the roles and in some cases the folder list that must be used for sessions where no users is logged in. For the specified site, no user has been specified, or the user has been deleted.
This means that the site is not accessible.
Access the administration interface for the specified site. Use the menu item Site Settings to specify an anonymous user for the site.