your recordset code does not use the ID querystring variable, it uses the FIRMID querystring variable:
$colname_rsFirmen = "-1";
if (isset($_GET['FIRMID'])) {
$colname_rsFirmen = (get_magic_quotes_gpc()) ? $_GET['FIRMID'] : addslashes($_GET['FIRMID']);
}
mysql_select_db($database_HPharm, $HPharm);
$query_rsFirmen = sprintf("SELECT * FROM firmen WHERE FIRMID = %s", GetSQLValueString($colname_rsFirmen, "int"));
$rsFirmen = mysql_query($query_rsFirmen, $HPharm) or die(mysql_error());
$row_rsFirmen = mysql_fetch_assoc($rsFirmen);
$totalRows_rsFirmen = mysql_num_rows($rsFirmen);
your link:
form.php?ID=3
should be:
form.php?FIRMID=3