Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at C:\Documents and Settings\Pc Alex\Desktop\host\gallomania.it\audio\ascolta.php: 1) in C:\Documents and Settings\Pc Alex\Desktop\host\gallomania.it\audio\ascolta.php on line 1

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at C:\Documents and Settings\Pc Alex\Desktop\host\gallomania.it\audio\ascolta.php: 1) in C:\Documents and Settings\Pc Alex\Desktop\host\gallomania.it\audio\ascolta.php on line 1

I miei dubbi sono due:
1- Perchè me lo scrive due volte se nella pagina c'è un solo session_start()???
2-Io l'ho messo in cima alla pagina..sopra ogni codice..perchè mi da errore?