function GetXmlHttpObject()
{
var xmlHttp=null;
try
  {
  // Firefox, Opera 8.0+, Safari
  xmlHttp=new XMLHttpRequest();
  }
catch (e)
  {
  // Internet Explorer
  try
    {
    xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
    }
  catch (e)
    {
    xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
    }
  }
return xmlHttp;
}

function stateChanged() 
{ 
if (xmlHttp.readyState==4)
{ 
eval(callCallback(xmlHttp));
}
}

var callCallback = null;
function callAjax(url, params, callback)
{
	callCallback = callback;
	xmlHttp=GetXmlHttpObject();
	
	if (xmlHttp==null)
	  {
	  alert ("Your browser does not support AJAX!");
	  return;
	  } 
	  
	if (params==''){
		params = '?';
	}else{
		params = '?' + params + '&';
	}
	  params += 'sid=' + Math.random();
	  
	 url += params;
	xmlHttp.onreadystatechange=stateChanged;
	xmlHttp.open("GET",url,true);
	xmlHttp.send(null);
}