When test processing a credit card, I get this error: "The referrer, relay response or receipt link URL is invalid"

I did a search on the archives and found this thread:
http://www.zen-cart.com/forum/showth...nk+URL+invalid

I use authorize.net - apparently it is not configured properly to return to my web site. But what I'm having trouble with is this: How do I find the correct address for my "Order Confirmation" page, so that I can configure authorize.net correctly?