function ajax_request(obj,url,wait_str,error_str,func)
{ 
var nowt=new Date();
var rnds = nowt.getHours()+""+nowt.getMinutes()+""+nowt.getSeconds()+""+nowt.getYear()+""+nowt.getMonth()+""+nowt.getDate()+""+nowt.getDay();
url=url+"&rand=" + rnds;
  var http_req;
 if (window.XMLHttpRequest) 
 {
 http_req=new XMLHttpRequest();
 //http_req.overrideMimeType('text/xml');
 } 
 else if (window.ActiveXObject) {
 http_req=new ActiveXObject("Microsoft.XMLHTTP");
 }
 if(obj!=""&&wait_str!="")document.getElementById(obj).innerHTML=wait_str;
 http_req.onreadystatechange = function(){
   if (http_req.readyState == 4) { //状态

   if (http_req.status == 200) { //成功返回
   if(http_req.responseText!=null && http_req.responseText!="")
   { 
     if(obj!="") document.getElementById(obj).innerHTML=http_req.responseText;
     func();
    }
    else
    {
        if(obj!="")document.getElementById(obj).style.display="none";
    }
   } 
   else { //返回不正常

     if(obj!=""&&error_str!="")document.getElementById(obj).innerHTML=error_str;
   }
  }
 };
     http_req.open("GET", url, true);
     http_req.send(null);
  }