Multiple websites

Can I use the same credit card payment gateway or merchant account, which ever you call it, for multiple sites? The sites are different in content and products to sell.

It depends on the tems of service of your merchant account provider or your payment gateway provider. In the case of 2CO, your account is good only for one website. If you would like to integrate 2CO into your other website, you need to apply for another account and pay the corresponding set up fee.