<script language="JavaScript">
    function opendiv_search_l2(id) {
        JsHttpRequest.query('search_form_l2.php?parent_id='+id, 
            {}, function(result, errors) {document.getElementById("search_l_2").innerHTML = errors; },false); 
        opendiv_search_l3(- 1 );
</script>			}

...

<select name="reg_l1" id="reg_l1" class="Xfield1"  style="width:100%;" onChange="javascript:opendiv_search_l2(this.value)"; >

    function opendiv_search_l2(id) {
        JsHttpRequest.query('search_form_l2.php?parent_id='+id, 
            {}, function(result, errors) {document.getElementById("search_l_2").innerHTML = errors; },false); 
        opendiv_search_l3(- 1 );
			}

    function opendiv_search_l3(id) {
        JsHttpRequest.query('search_form_l3.php?parent_id='+id, 
            {}, function(result, errors) {document.getElementById("search_l_3").innerHTML = errors; },false); }

<?php
require_once "lib/JsHttpRequest/JsHttpRequest.php";
$JsHttpRequest =& new JsHttpRequest("windows-1251");
?>

<?php require_once('Connections/realestatedb.php'); ?>
<?php
$tmp_id=$_GET['parent_id'];
$tmp_value_all='';
mysql_select_db($database_realestatedb, $realestatedb);
$query_Recordset2 = "select * from region where parent_id=$tmp_id  order by name, xorder";
$Recordset2 = mysql_query($query_Recordset2, $realestatedb) or die(mysql_error());
$row_Recordset2 = mysql_fetch_assoc($Recordset2);
$totalRows_Recordset2 = mysql_num_rows($Recordset2);
if ($totalRows_Recordset2> 0 ) {
?>
<?

$chg_evt_handler = (PMA_USR_BROWSER_AGENT == 'IE' && PMA_USR_BROWSER_VER >=  5 )
                 ? 'onpropertychange'
                 : 'onchange';

?>

              <select name="reg_l2" id="reg_l2" class="Xfield1"  style="width:100%;" <?php echo $chg_evt_handler; ?>="javascript:opendiv_search_l3(this.value)";>
                <?php
do {  
?>
                <option value="<?php echo $row_Recordset2['id']?>"<?php if (!(strcmp($row_Recordset2['id'], $row_Recordset2['id']))); if ($tmp_value_all<>'') {$tmp_value_all=$tmp_value_all.',';};  $tmp_value_all=$tmp_value_all.$row_Recordset2['id'];  ?>><?php echo $row_Recordset2['name']?></option>
                <?php
} while ($row_Recordset2 = mysql_fetch_assoc($Recordset2));
  $rows = mysql_num_rows($Recordset2);
  if($rows >  0 ) {
      mysql_data_seek($Recordset2,  0 );
	  $row_Recordset2 = mysql_fetch_assoc($Recordset2);
  }
?>              
                <option value="<? echo $tmp_value_all; ?>" selected="selected">╚ёърЄ№ тхчфх</option>
              </select>

<?php
}
mysql_free_result($Recordset2);
?>

document.getElementById("reg_l2").Focus();