where is the error? - Page 1

I can't find the error.
Maybe someone can help me...


$Y=mysql_fetch_array(mysql_db_query($Xdb, "SELECT * FROM mod_temp WHERE
id='".$_POST['conten']."'"));

$Y['contenuto'] is a html code

$contenuto = file_get_contents(SITO_2.'inc/html2pdf/_tcpdf_5.0.002/cache/utf8test.txt');
$contenuto = '<page>'.$Y['contenuto'].'</page>';
require_once(SITO_2."inc/html2pdf/html2pdf.class.php");
try{
$html2pdf = new HTML2PDF('P', 'A4', 'it');
$html2pdf->setModeDebug();
$html2pdf->setDefaultFont('Arial');
$html2pdf->writeHTML($contenuto);
$html2pdf->Output('mandato.pdf');
}
catch(HTML2PDF_exception $e) {
echo $e;
exit;
}

This is the error:

TCPDF ERROR: Some data has already been output, can't send PDF file

You need to turn on your PHP error reporting. If there is any error printed out before the PDF document then it would not work.