var xmlHttp;

function GetXmlHttpObject(handler)
{
  var objXmlHttp=null;

  if (navigator.userAgent.indexOf("Opera")>=0)
  {
    alert("This example doesn't work in Opera");
    return objXmlHttp;
  }
  if (navigator.userAgent.indexOf("MSIE")>=0)
  {
    var strName="Msxml2.XMLHTTP";
    if (navigator.appVersion.indexOf("MSIE 5.5")>=0)
    {
      strName="Microsoft.XMLHTTP";
    }
    try
    {
      objXmlHttp=new ActiveXObject(strName);
      objXmlHttp.onreadystatechange=handler;
      return objXmlHttp;
    }
    catch(e)
    {
      alert("Error. Scripting for ActiveX might be disabled");
      return objXmlHttp;
    }
  }
  if (navigator.userAgent.indexOf("Mozilla")>=0)
  {
    objXmlHttp=new XMLHttpRequest();
    objXmlHttp.onload=handler;
    objXmlHttp.onerror=handler;
    return objXmlHttp;
  }
  return objXmlHttp;
}