//---- this function is a wrapper for XMLHttpRequest and is not mine (although I use it for years)
function XHConn()
{
	var xmlhttp, bComplete = false;
	try { xmlhttp = new ActiveXObject("Msxml2.XMLHTTP"); }
	catch (e) { try { xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); }
	catch (e) { try { xmlhttp = new XMLHttpRequest(); }
	catch (e) { xmlhttp = false; }}}
	if (!xmlhttp) return null;
	this.connect = function(sURL, sMethod, sVars, fnDone)
	{
	  if (!xmlhttp) return false;
	  bComplete = false;
	  sMethod = sMethod.toUpperCase();
 
	  try
	  {
		if (sMethod == "GET")
		{
		  xmlhttp.open(sMethod, sURL+"?"+sVars, true);
		  sVars = "";
		}
		else
		{
		  xmlhttp.open(sMethod, sURL, true);
		  xmlhttp.setRequestHeader("Method", "POST "+sURL+" HTTP/1.1");
		  xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
		}
		xmlhttp.onreadystatechange = function()
		{
		  if (xmlhttp.readyState == 4 && !bComplete)
		  {
			bComplete = true;
			fnDone(xmlhttp);
		  }
		};
		xmlhttp.send(sVars);
	  }
	  catch(z) { return false; }
	  return true;
	};
 
	return this;
}
 
//---- we make a call to load categories.xml file found in the same folder as the current page
//---- and we forward the response to be processed by a callback function called "procGetCategories"
function getCategories()
{
	var ajaxConn  = new XHConn();   
	sParams 	  = "";
	ajaxConn.connect("http://"+window.location.hostname+"/categories.xml", "GET", sParams, procGetCategories);
}
 
function procGetCategories(objReturn)
{
    xmlDoc = null;
 
	try //Internet Explorer
	{
		xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
		xmlDoc.async="false";
		xmlDoc.loadXML(objReturn.responseText);
	}
	catch(e) // all the others (Opera I'm not sure though .... never tested this on Opera)
	{
		parser = new DOMParser();
		xmlDoc=parser.parseFromString(objReturn.responseText,"text/xml");
	}
 
	var root = xmlDoc.childNodes[0];
	var catName;
	var catId;
	var x=root.childNodes; //---- categories node in my case
 
	for (i=0;i<x.length;i++)
	{
		if (x[i].nodeType==1)
		{
			catId   = x[i].childNodes[0].childNodes[0].nodeValue;
			catName = x[i].childNodes[1].childNodes[0].nodeValue;
 
			//---- here you can do whatever you want with the received data. I chosed to create some buttons using "createCategButton" function
			createCategButton(catId, catName);			
		}
	}   	
}