"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.
Marti Mullen commented
I agree this is a really important change but see it as a little bit bigger issue than just continue shopping. We have pages that are not tied to the main navigation so we can present a store for a special event or sale. There are 3 pages in the store that are system pages we can see and edit but the rest of them, once checkout begins, are inaccessible to us. I essentially can't use any navigation, not main navigation, not breadcrumb navigation, without the user being able to get out of the special store pages. The continue shopping is critical. But also, feedback when the user puts an item in the cart needs to be better - most people will not think anything happened when they do add to cart and all that happens is the very tiny cart gadget increments.
Robert Sylvester commented
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.