//显示产品页面的活动广告信息
function product_ad_list_ajax(str){
	delete xmlhttp ;
	var xmlhttp;
	if (xmlhttp==null || typeof(xmlhttp)!="object"){
		try{
			xmlhttp= new ActiveXObject('Msxml2.XMLHTTP');
		}catch(e){
			try{
				xmlhttp= new ActiveXObject('Microsoft.XMLHTTP');
			}catch(e){
				try{
					xmlhttp= new XMLHttpRequest();
				}catch(e){}
			}
		}
	}
	xmlhttp.onreadystatechange=function(){
		var i=0;
		if (4==xmlhttp.readyState){
			if (200==xmlhttp.status){
				var return_value=xmlhttp.responseText;
				if (return_value != null & return_value != ""){
					document.getElementById("product_ad_list").innerHTML = return_value;
				}
			}
		delete xmlhttp ; 
		xmlhttp=null;
		CollectGarbage;
		}
	}
	xmlhttp.open("post", "/ajax_product_ad_list.php", true);
	xmlhttp.setRequestHeader("CONTENT-TYPE","application/x-www-form-urlencoded;text/xml;charset=utf-8");
	xmlhttp.send("act="+str);
}