within SharePoint if an error occurs we would be receiving quite an unhelpful
error message i.e. “An unexpected error has occurred”. It is because by default
the detailed error messages are turned off for security reasons.
the steps for getting the full error messages
to the SharePoint site for which you would like to enable it.
Most likely to be found at c:\inetpub\wwwroot\wss\VirtualDirectories\...
and a sub directory with your web application’s port number.
and open the web.config file for editing.