var http_request = false;
 function send_request(url) {//初始化、指定处理函数、发送请求的函数
  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;

  // 确定发送请求的方式和URL以及是否同步执行下段代码
  http_request.open("GET", url, false);
  http_request.send(null);
 }


 // 处理返回信息的函数
    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
                //alert(http_request.responseText);
				document.getElementById(currentPos).innerHTML = http_request.responseText;
            } else { //页面不正常
                //alert("您所请求的页面有异常。");
            }
        }
    }

 //调用ajax函数
 function ajax_get(url,obj) {
  document.getElementById(obj).parentNode.style.display = "";
  //document.getElementById(obj).innerHTML = "正在读取数据..."
  currentPos = obj;
  send_request(url,obj);
 }