I have been working on google checkout integration in classic ASP, my client have various eCommerce websites and want to use single merchant account (Google Checkout) for all websites. I have set up the callback url in merchant account, but I need to identify from which website's order has been placed, to save information in the database.
Can I specify a callback url from the code itself, for each different website using the single merchant account?
You can use the merchant-private-data field to pass any custom data about your order (including the website info).
When you get back the notification, read the custom info from the merchant-private-data field and identify from which website it originated.
See this answer for a solution to a similar issue.