session_start(); не работает

session_start();почему то выдает ошибкуWarning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at Z:\home\91.216.165.69\www\1.php:5) in Z:\home\91.216.165.69\www\1.php on line 6Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at Z:\home\91.216.165.69\www\1.php:5) in Z:\home\91.216.165.69\www\1.php on line 6вопрос почему и как исправить?спасибо наперед