ecco come lo modificato:

function CreateXmlHttpRequest(){
var xmlhttp=null;
try{
xmlhttp=new XMLHttpRequest();
}catch(e){}
try{
xmlhttp= new ActiveXObject("Msxml2.XMLHTTP");
}catch(e){}
try{
xmlhttp= new ActiveXObject("Microsft.XMLHTTP");
}catch(e){}
return xmlhttp
}

function radioreload(){
var request=CreateXmlHttpRequest();
request.open("POST","reloadradio.php");
request.send(null);
if(request.readyState==4 && request.status==200){
var risultato=request.responseText;
var elemento=document.getElementById("divradio");
elemento.innerHTML=risultato;
}
}

<div id="divradio">...</div>

ma nulla non va