http://zqktlwk5ilgohy63eyrptyb4mc76bunfmxcnstkmveyjnskxkpq3b5yd.onion/wiki/index.php/Main_Page
Services can go down temporarily, so we keep track of when they do and maintain a list of dead hidden services. In addition to an onion simply being gone (Tor cannot resolve the onion), sites that display 404 (and use a known onion/URL based hosting service) are the only other thing that is considered truly DOWN.