ผมใช้ fancybox ซึ่งอยู่ใน <div id='test' name='test'></div> ไม่ได้ครับ

<select name='a' id='a' onchange='data_show(this.value,'a');'>
//---------ข้อมูล
</select>
<div name='a' id='a'></div>

<script language="javascript">

function uzXmlHttp(){
    var xmlhttp = false;
    try{
        xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
    }catch(e){
        try{
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }catch(e){
            xmlhttp = false;
        }
    }
 
    if(!xmlhttp && document.createElement){
        xmlhttp = new XMLHttpRequest();
    }
    return xmlhttp;
}
// End XmlHttp Object

function data_show(select_id,result){
	var url = 'xx.php?select_id='+select_id+'&result='+result;
	//alert(url);
	
    xmlhttp = uzXmlHttp();
    xmlhttp.open("GET", url, false);
	xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=TIS-620"); // set Header
    xmlhttp.send(null);
	document.getElementById("a").innerHTML =  xmlhttp.responseText;
}
</script>

	<script type="text/javascript" src="scripts/jquery-1.4.3.min.js"></script>
	<script type="text/javascript" src="fancybox/jquery.mousewheel-3.0.4.pack.js"></script>
	<script type="text/javascript" src="fancybox/jquery.fancybox-1.3.4.pack.js"></script>
	<link rel="stylesheet" type="text/css" href="fancybox/jquery.fancybox-1.3.4.css" media="screen" />

	<script type="text/javascript">
		$(document).ready(function() {

			$('a[id^="popupwin"]').fancybox({
				'width'				: '95%',
				'height'			: '95%',
				'autoScale'     	: false,
				'transitionIn'		: 'none',
				'transitionOut'		: 'none',
				'hideOnOverlayClick': false,
				'type'				: 'iframe',
				onClosed	:	function() {
				}
			});
	
		});
	</script>
<a href='yy.php' class='various iframe' id='popupwin'>เพิ่มข้อมูล</a>