Why would I get this error?

#1

Server Error in ‘/’ Application.

Runtime Error

Description: An exception occurred while processing your request. Additionally, another exception occurred while executing the custom error page for the first exception. The request has been terminated.

#2

Is there Database involved in your project ?

#3

You need to open ASP.NET debug mode to see the real error:

https://msdn.microsoft.com/en-us/library/e8z01xdh.aspx