Session Registering

Im using session in my form, there are 6 pages to the form, It all works fine, until You work your way back through the form, to ammend the filled in details. e.g - If I go to page 1, and fill out my name, and post to the next page, heres the code Im using: PHP:------------------------------------------------------------------------ -------- <form method="post" action="page2.php"> <input type="text" name="firstname" value="<?=$_SESSION['firstname'];?>"> </form> ---------------------------------------------------------------------------- ---- Its registered on the top of page2 with the following code: PHP:------------------------------------------------------------------------ -------- session_start(); $_SESSION['firstname']=$_POST['firstname']; ---------------------------------------------------------------------------- ---- That works fine, I have a link on all my pages that links back to the previous page e.g <a href="page1.php">Go Back</a> If I go back to the first page, from the second page the fields are populated fine, but If i continue onto page3.php then go back page1.php is no longer populated!! Any Ideas why this is happening?? and If so a remedy, Is it a code issue or a conf Issue?? Thanks C