If you have trouble with Internet Explorer 6 and non-working sessions (all session-data is lost after clicking on a link), please look user-hints for setcookie().
You have to add the following line after session_start() to get sessions working:
Código PHP:
<?php
// Initalize session
session_start();
// Send modified header
header('P3P: CP="NOI ADM DEV PSAi COM NAV OUR OTRo STP IND DEM"');
?>