"Continue Shopping" Link
There needs to be a "continue shopping" link from the cart and from each item to that you back to the online store. Right now, if you click the "back" in the browser, you get back to the store, but that is not obvious to the user. In most online stores, there is a "continue shopping" link in the cart that allows you to go back to the online store.
I agree, the continue shopping button should bring you back to the store/catalog, not the last purchase. It should also be on each product page, as well as the cart.
Make it editable and make it a gadget.