pnlCreditCardPane is in checkoutpayment.aspx, but if you're trying to change the table structure what you're going to find is that inside of pnlCreditCardPane is a Literal called CCForm which is populated from the codebehind (checkoutpayment.aspx.cs) by a call to BillingAddress.InputCardHTML. This is where the table html structure is built. To modify this, you'll need to open the ASPDNSFCore/Address.cs file and find the InputCardHTML method (in version 8.0.1.2 it's around line 1820).
<a href="http://www.aspdotnetstorefront.com">Shopping Cart Software</a>