ti riposto il codice :

<?php
$data = date ("d. M. Y");
$username = $_GET ['login'];


//controllo accesso
include ("dbconnect.php");


$check = mysql_query ("select password, username from accesso") or die (mysql_error());
while ($row = mysql_fetch_array($check))

{
$user = $row[username];
}

if ( $user <> $username )

header ("Location: http://localhost/accesso.php");

?>

//poi faccio partire i tag HMTL
<html>

<head> etc etc etc
...

</html>