If you want to add a simple shopping cart to your site, this is a good start.   It keeps track of returning users without using cookies.   They check off items on your pages then click "add to cart. "  It will add shipping etc. to the final total, then when they click "purchase", you are notified.   Their email is sent to you so you can contact them about payment. To deploy, simply add a checkbox code to each item on your site.