Session Erro

[phew 0]

Estou usando login com session + iframe... E todas as paginas que abrem no ifram dão o seguinte erro:

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at c:\bin\easyphp1-8\www\admin\home_not.php:5) in c:\bin\easyphp1-8\www\admin\verifica.php on line 3

Verifica.php

<?phpsession_start();if( !$_SESSION['authorized'] ){   header("Location: index.php");}?>

[augustogava 0]

session_start();tem q estar na primeira linha, antes de tudo!