function __construct(&$session, $pages, $conf = array())
 {
     self::$session = $session;
     self::$pages = $pages;
     if (!$conf) {
         $conf = self::default_conf();
     }
     //always override this option
     //for smooth navigation
     $conf['strict_navigation'] = 1;
     //please
     self::$conf = $conf;
 }