This can be a little dicey when AJAX was used to render the form that you're thinking about submitting; for a browser to Do It Right they may need to cache complicated stuff like (a) the entire DOM and (b) the entire state of the JS interpreter at the moment navigation began away from the page. Even if we only do this on backwards navigation and immediately trash it when we navigate forwards to a new location, it still sounds to a developer's ear like a memory leak waiting to happen. It might be mitigated if you store no more than, say, 10 pages back.