Service Unavailable. HTTP Error 503. The service is unavailable
Sometimes the SharePoint 2007 configuration goes crazy all of a sudden and you end up with a non working server farm installation showing “Service Unavailable. HTTP Error 503. The service is unavailable” instead of your sites.
This can happen if the SharePoint app pool stop due to a crash. In this post, I’ll show you a little trick to restart the application pool and fix the SharePoint HTTP 503 Error.
Fix Sharepoint 503 Error
If you get this message after typing your SharePoint Site URL, go to Internet Information Services (IIS) Manager and then look under Application Pools to make sure that your SharePoint application pools are started correctly and restart the stopped ones if any. If you still get the SharePoint HTTP 503 error while accessing SharePoint, right click the stopped application pools, choose Advanced settings and retype the identity and password. Start the stopped SharePoint applications pools and try accessing your site again.
If none of this worked, run the SharePoint Products and Technologies Configuration Wizard and choose Do not disconnect from this server farm. This should fix the SharePoint 503 error.