Secura – AJAX Cart is a powerful system which can be integrated to new/old HTML websites to extend their functionality as a Cart with downloadable products. You can now sale your digital products right from your old HTML website. You don’t need to use OpenCart or any other cart for your e-commerce website. You can create your own e-commerce website in minutes using this Cart system.

Demo: http://codecanyon.net/item/ajax-cart-for-html-websites-with-digital-products/4903762