請幫忙呢個js 有問題??

我的防毒成日出左話呢個係木馬程式
應該如何更改???

Thanks

//?建xmlhttp函?
function createAjaxObj(){
var httprequest=false
if (window.XMLHttpRequest){ // if Mozilla, Safari etc
  httprequest=new XMLHttpRequest()
  if (httprequest.overrideMimeType)
httprequest.overrideMimeType('text/xml');
}
else if (window.ActiveXObject){ // if IE
  try
  {
httprequest=new ActiveXObject("Ms"+"xml2."+"XMLHTTP");
  }
  catch (e)
  {
try
{
httprequest=new ActiveXObject('Micro'+'soft.'+'XMLHTTP');
}
catch (e){}
  }
}
return httprequest;
}

//利用xmlhttp?取?据函?,????，第一?是?理url,第二??返回?据
function load_Hits(do_url){
var xmlhttp = createAjaxObj();
try
{

  var params=do_url;

  xmlhttp.abort();

  xmlhttp.open("get",params,true);

  xmlhttp.setRequestHeader("Content-type", "text/html;charset=gb2312");

  xmlhttp.setRequestHeader("If-Modified-Since","0");

  xmlhttp.setRequestHeader("Content-length", params.length);

  xmlhttp.setRequestHeader("Connection", "close");

  xmlhttp.onreadystatechange=f //?置f?返回?据?理函?

  xmlhttp.send(null);

}catch(ex){alert(ex)}

//?据返回?理函?
  function f()
{

if(xmlhttp.readyState!= 4 || xmlhttp.status!=200 )
return ;
var b= xmlhttp.responseText;
document.getElementById("hits").innerHTML="";
document.getElementById("hits").innerHTML=b;
}
}