function getXHR() {
var xmlHttp = null;
if (window.XMLHttpRequest) {
  // If IE7, Mozilla, Safari, and so on: Use native object.
  xmlHttp = new XMLHttpRequest();
}
else
{
  if (window.ActiveXObject) {
     // ...otherwise, use the ActiveX control for IE5.x and IE6.
     xmlHttp = new ActiveXObject('MSXML2.XMLHTTP.3.0');
  }
} 
return xmlHttp;
}