ajax问题,写出东东只能在IE正常,在netscape,firefox不正常,是js读不出返回的xml格式数据.

Question

http://search.chinacars.com/html/722/quanguo_722_1.htm点击某个地区,在IE下正常,在在netscape,firefox不正常,已经找到原来,但不会修改.是js读不出返回的xml格式数据.
返回的xml格式如下:http://search.chinacars.com/html/listcompany.aspx?cartype_id=1994&province=0&city=0js代码如下:var http_request = false;
 function loadXMLDoc(url) {
http_request = false;                if (window.XMLHttpRequest) { // Mozilla, Safari,...
                    http_request = new XMLHttpRequest();
                    if (http_request.overrideMimeType) {
                        http_request.overrideMimeType('text/xml');
                    }
                } else if (window.ActiveXObject) { // IE
                    try {
                        http_request = new ActiveXObject("Msxml2.XMLHTTP");
                    } catch (e) {
                        try {
                        http_request = new ActiveXObject("Microsoft.XMLHTTP");
                        } catch (e) {}
                    }
                }                if (!http_request) {
                    alert('Giving up :( Cannot create an XMLHTTP instance');
                    return false;
                }
                http_request.onreadystatechange = alertContents;
                http_request.open('GET', url, true);
                http_request.send(null);            }            function alertContents() {                if (http_request.readyState == 4) {
                    if (http_request.status == 200) {
                        handleResult();
                    } else {
                        alert('There was a problem with the request.');
                    }
                }function handleResult() {

//Get item node from xml result.
var xmldoc = http_request.responseXML;
var items = xmldoc.getElementsByTagName('root');

var listspan=items.item(0).firstChild.data;

alert(listspan);

//alert(items.item(0).firstChild.xml);

var oNodes=items.item(1).childNodes;
var sTrHtml="";
for(var j=0;j<oNodes.length;j++){
sTrHtml +=oNodes[j].xml;
}

alert(sTrHtml);//此处出了问题，得不到xml格式数据，但是在IE下面正常,是不是其它游览器和IE读出xml的语法不一样?

document.getElementById(listspan).innerHTML=sTrHtml;
var listdiv=items.item(2).firstChild.data;

//屏蔽原始标记
document.getElementById(listdiv).style.display="none";


}