var url="";
function send_request(url) { 
http_request = false;
//开始初始化XMLHttpRequest 对象
if(window.XMLHttpRequest) { //Mozilla 浏览器
   http_request = new XMLHttpRequest();
   if (http_request.overrideMimeType) {//设置MiME 类别
   http_request.overrideMimeType("text/xml");
   }
}else if (window.ActiveXObject) { // IE 浏览器
   try {
    http_request = new ActiveXObject("Msxml2.XMLHTTP");
   } catch (e) {
    try {
     http_request = new ActiveXObject("Microsoft.XMLHTTP");
    } catch (e) {}
   }
}
if (!http_request) { // 异常，创建对象实例失败
   window.alert("不能创建XMLHttpRequest 对象实例.");
   return false;
}
http_request.onreadystatechange = processRequest;

http_request.open("GET", url, true);
http_request.send(null);
}


function processRequest() { 
if (http_request.readyState == 4) { // 判断对象状态
   if (http_request.status == 200) { // 信息已经成功返回，开始处理信息
document.getElementById("topclass").innerHTML=http_request.responseText;
   
   }
else { //页面不正常
   alert("nothing return 200");
   }
}else{
   document.getElementById('dao_01').style.display="";
document.getElementById('dao_02').style.display="";
   document.getElementById('topclass').innerHTML = "<span id=loading >加载中...</span>";

}
}

function GetTopClass(id)
{
send_request("/ajax_top.aspx?t="+id);
}