catdownload.php (line 16)
$sql = ('SELECT * FROM downloads WHERE categorie='.$categorie.''); 

download.php (line 6)
mysql_query('SELECT * FROM `downloads`  WHERE categorie=' . $_GET['id']);

hitcounter.php (line 15)
$requete = "SELECT lien FROM downloads WHERE id=$id";


download:
http://www.01php.com/fiche-scripts-148.html