Question: I know I can create a custom event and associate data with it and retrieve it in respective Event Listener. But What I am interested to know is, is there a short method (without having to extend Alert Event Class) to associate parameters to its alert Listener.

Answer: 
`.ASP` is traditionally not a .NET application page unless you re-configured the `.ASP` extension.

My guess is that you do not have `.ASP` enabled and the server thinks "main.asp" is a virtual directory not a .ASP page:

[Enabling ASP Pages in IIS 6.0](http://technet.microsoft.com/en-us/library/cc737992%28WS.10%29.aspx)
It means that you can only rewrite to another virtual path, meaning /somefolder/somefile.asp or aspx or whatever.

If you want to execute the asp page from another server and just serve the content it generates, you will need to "proxy" that page. That can be a .aspx page that makes a remote request or a proxy module for asp.net. I don't know of any, but I'm guessing there is one.