$pwd = md5(md5($password));
    $MySql = "SELECT * FROM utenti WHERE username='$username' AND password='$pwd'";
    $Result = mysql_query($MySql);
    $rs = mysql_fetch_array($Result);
    $a1 = $rs['username'];
    $a2 = $rs['password'];
    $rs->close;
if((!$a1) && (!empty($username))){
print("<script>alert(\"Username inesistente\")</script>");
} elseif(($a2 != $pwd) && (!empty($password)))  {
print("<script>alert(\"Password Errata\")</script>");