Session Problem (Design problem!?)

I got this strange problem, maybe a design flaw, please look at it and tell me what's wrong. 3 files in total 1.php3 ---------------------------------- <?php session_start(); ?> <html> <FORM action="./2.php3" method="post"> <P> <input name="var" type="text"><br> <INPUT type="submit" value="Send"> </FORM> </html> ---------------------------------- 2.php3 ---------------------------------- <?php session_start(); ?> <html> <? session_unregister("var"); print $var; print "<A HREF=\"./3.php3?var=$var\">GO</A>"; ?> </html> ----------------------------------- 3.php3 ----------------------------------- <?php session_start(); ?> <html> <? session_register("var"); print $var; ?> </html> ------------------------------------ When I goto 1.php3 and type in something in the text field, then goto 2.php3 and click go, it automatically goto 3.php3 with data that I type in 1.php3. The problem starts when I click BACK button on the browser to 1.php3 and type in another data and click the button on the form again, but here is the trouble. I seems to be getting the data I type in First, not the current one. By using phpinfo(), I cannot find the data are all up to date, I wonder how this data still ends up sitting there. Can anyone tell me what's going on? BTW, going back once again with the second set of data and proceed to 2.php3 seems fine. Could it be cache of browser?