Warning: require_once(classes/db.class.php): failed to open stream: No such file or directory in /var/www/mobi/public/calendar.php on line 2

Fatal error: require_once(): Failed opening required 'classes/db.class.php' (include_path='.:/usr/share/pear:/usr/share/php') in /var/www/mobi/public/calendar.php on line 2