IIS server returns the error:
description: This error (HTTP 500 Internal Server Error) means that the website you are visiting had a server problem which prevented the webpage from displaying.
All the websites on that IIS server stopped working.
that means it's an internal error, meaning internal to the service - the service threw an exception that was not caught. you should try checking whats the error:
1.Check Windows event logs on the server to see whats the full exception.
2.There might be an issue in the way you have hosted your app. May be multiple config files?
Do make sure, you have hosted your application correctly. Published the application as website and setting up the virtual directory.