Server Application Unavailable

The web application you are attempting to access on this web server is currently unavailable.  Please hit the "Refresh" button in your web browser to retry your request

Resolution:

We've found this is typically received after changing ASP.NET versions (from 1.1 to 2, or vice versa).  The solution is to simply stop and start the application pool - please submit a support request referencing the error and this KB article if you are receiving this message.