Validate Incomming Request from Other Site

[Prabhat]

Hi all,

I have one Page "page1.asp" in my website "www.mysite.com" that should open
only if it is requested from a another site "www.site2.com" with one ID as
parameter (may be querystring - Encrypted). Even the page1.asp should not
get open of requested from within the mysite.com.

How do I implement this and what are all validation I need in the top of
page1.asp. Please suggest.

Thanks
Prabhat