To do what you're asking, you can get the previous page, the referrer, through php, like this:
$referer = $_SERVER["HTTP_REFERER"];
You can then pass the $referer variable to a script to dynamically generate a link to go to the previous page. If you do this, the browser will not remember form data. Furthermore, this method will only work to go back one page - for example, if you are on page a, then you go to page b, then page c, then you click your special back button you will be taken to page b, just as intended. If you click it again, though, you will be taken to page c, not page a, because page c was the previous page. Both of these problems can be solved, but would require much fancier php.
Note that "referrer" in $_SERVER["HTTP_REFERER"] is spelled incorrectly - it's supposed to be. Spell it correctly and it won't work.
