Going back into the history.

Alright, I understand the differnce between php (server-side) and js (client) so don't bitch about this question and point out the obvious... :) I've noticed that when I create pages with php that at times I cannot go back w/o resubmitting form data. But so far I haven't really been able to uncover a pattern in when this happens and when it doesn't. Some forms I make seem to make me want to resubmit if I go back on the browser, and some do not. Can anyone explain where this happens and where this does not. Second. Could this potentially be solved (provided that the explanation for part 1 doesn't take care of it) by using php to parse that last request and use javascript to insert the previous request to insert into the history. ie If previously I submitted a form with certain elements, use php to parse that data, and use a javascript function, possibly linked to onLoad, to insert the previous request into the history. If that is an acceptable way to solve that problem, what is the easiest way to do that. $REQUEST_URI does not store the form elements, unless they are specifically typed out in the URL. So I'm thinking I would just have to parse the $GLOBALS array and insert that data into a the old link. Basically my question is, is there an easier way to do what I want to do? Is there some way that I can write my scripts so that you don't have expired pages when you try to go back in the browser history? Will I need to resubmit all the time even if I do this? (Logic tells me know, but sometimes my logic isn't the correct logic... lol) Ben