Explain the three main components of the ATL Server project - the Web application DLL, the ISAPI extension DLL, and the server response file.

There can be many Web application DLLs in a virtual directory which can provide one or more named request handlers.
They have the functionality for handling requests and generating responses.
They expose request handlers that communicate with the ISAPI extension DLL.
Each Web application DLL can be used from multiple server response files.
Server response files are basically text files.
They contain the static parts of a response and special tags.
These special tags describe where request handler methods can be called to generate the dynamic parts of the response.
Each server response file can use more than one Web application DLL.
The requests from IIS are received by the ISAPI extension DLL and are passed to the appropriate Web application DLL.
It provides the request handling infrastructure and common services used by the Web application DLLs.
One ISAPI extension DLL exists per virtual directory and it handles requests for files with the .dll and .srf extensions.