If you find yourself having trouble accessing cotent or using your site as an anonymous user, you can safely run the following queries against your Drupal DB (4.6/4.7):
INSERT INTO users (uid, name, mail) VALUES ('0', '', '');
INSERT INTO users_roles (uid, rid) VALUES (0, 1);
INSERT INTO node_access VALUES (0, 0, 'all', 1, 0, 0);
If any of the queries above returns a "duplicate entry" error, that means a row already exists, and that table is already OK.
Tuesday, October 19, 2010
Re-creating user 0 fixes inaccessible Drupal site
Devbee explains why user 0, the default user is so important in Drupal. A missing user 0 can mean that your site cannot be reached from the outside!