Using Romancart with Paypal. How does Paypal know what website.

The transaction has come from, if you're using a 3rd party gateway like a shopping cart (Romancart) to take the sale, it then redirects to Paypal for the payment to be made.
I recently had my paypal account limited because they said I was in violation of their user terms as they determined the website to be unlawful. So the question is, how do they know which website I am using since there is an intermediate 3rd party involved? I also have had it on the website for a year now, how is it only now they limit it. Anyone know much about Shopping carts linked with Paypal?