link in form

Goeden middag, met dit linkje
echo "" . '<a href="Adres_id.php"'.$data['adres_id'].'">'.'Gegevens'.'</a>';

roep ik dit script aan
<? $server = "localhost"; $user = "root"; $database = "balansadvies";


Mysql_connect ($server, $user); mysql_select_db($database);




$sql =
"SELECT bdrnaam,
titel,
naam,
adres,
postcode,
plaats,
prov,
telefoon,
mobiel,
mail,
ini,
fax
FROM adres
WHERE adres_ID = ".intval($_GET['adres_id']);






$result = mysql_query($sql); while( $data = mysql_fetch_array($result))
{



echo "<center><table width='560' border=1 style='background-color:#FFEE99'><tr><td><center><h2>". $data['bdrnaam'] . "</h2></center></table>";
echo "<table width='70%' ><tr><td align='right'>". $data['titel'] . ":". $data['ini']. "&nbsp". $data['naam'] . "<br>". $data['adres'] . "<br>". $data['postcode'] . "<br>". $data['plaats'] . "-". $data['prov'] .
"</td><td width='50%' align='left'>&nbsp&nbspTelefoonnummer:&nbsp". $data['telefoon'] . "<br>&nbsp&nbspFaxnummer:&nbsp". $data['fax'] . "<br>&nbsp&nbspMobielnummer:&nbsp". $data['mobiel'] . "<br>&nbsp&nbspE-mailadres:". '<a href="mailto:'.$data['mail'].'">'.
$data['mail']."</a></table></tr></td></center>";



}


maar ik krijg steeds
deze storing
Notice: Undefined index: adres_id in c:\program files\easyphp1-7\www\balansadvies\adres_id.php on line 23


?>

kan iemand mij helpen