Most of the time, when you use the back button on a page containing a form, your results are erased. This page will remember your choices for up to an hour, even if you close the browser and reopen it. As soon as the page loads, it looks up the stored values and changes the form to match. At the moment it doesn't do anything more with the information -- you can't even submit the form -- but that's not the point. This sort of arrangement is useful for pages that store user preferences, which can then be read by any other page on your site.