Buonasera,
mi capita questo errore ....

Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at /home/mhd-01/www.francescopassanante.com/htdocs/index.php:1) in /home/mhd-01/www.francescopassanante.com/htdocs/index.php on line 2

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/mhd-01/www.francescopassanante.com/htdocs/index.php:1) in /home/mhd-01/www.francescopassanante.com/htdocs/index.php on line 2

non capisco come mai, la linea 2 della pagina index.php è la seguente:

codice:
<?php
session_start();   ------> LINEA 2
if (!isset ($_SESSION['lang'])){ $_SESSION['lang'] = 'it' ;}
isset($_GET['lang']) ? $lang = $_GET['lang'] : $lang = $_SESSION['lang']; 
$_SESSION['lang'] = $lang;
require("{$lang}.php");
?>