If you're smart about the style/display format, this can be done with a frame that only has the necessary markup (ie just the contents of the cart, with links, think a sidebar/pop-up shopping cart embedded in the middle of the page). You can avoid the flash with css page transitions, too. It's not as nice as scripted setup, but if you're on a decent connection (latency) it's about even with other forms of progressive enhancement since you're not loading an entire UI framework. I'm not sure how well this would work for accessibility though, plain old frames aren't used much anymore.