I am trying to set up an E-Commerce site for my mother using Zen-Cart. (I have designed/developed many sites, but never an E-Commerce) Anyway, I am using Google Checkout. I have the SSL. But now I am getting a message that I need a API callback URL....
I am not sure what one is, what I need to do to set it up, or where to set it up, or even how to set it up.... Can someone point me in the right direction?