var xhr = createXHR(); // cross browser XHR creation

function createXHR()
{
  try { return new XMLHttpRequest(); } catch(e) {}
  try { return new ActiveXObject("Msxml2.XMLHTTP.6.0"); } catch (e) {}
  try { return new ActiveXObject("Msxml2.XMLHTTP.3.0"); } catch (e) {}
  try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) {}
  try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) {}
  alert("XMLHttpRequest not supported");
  return null;
}

function stateChanged() {
  if (xhr.readyState==4) {
    if (xhr.status==200) {// 200 = Response Error Free                
      document.getElementById("section_item").innerHTML="";
      document.getElementById("ajax_section_item").innerHTML=xhr.responseText;
      var pic = document.getElementById( 'loadingImg' );      
      pic.src = "";
      document.getElementById( 'loadingImg' ).style.display = "none";
    } else {
      alert("Problem retrieving XML data");
    }
  } else if(xhr.readyState == 1) {
    var pic = document.getElementById( 'loadingImg' );
    pic.src = "http://www.atwebbay.com/images/common-sites/ajax-loader.gif";
    centerElementOnScreen(pic);
    pic.style.display = "block";
  }                    
}

function centerElementOnScreen(element)
{
   var scrollTop = document.body.scrollTop;
   var scrollLeft = document.body.scrollLeft;
  
   var viewPortHeight = document.body.clientHeight;
   var viewPortWidth = document.body.clientWidth;
  
   if (document.compatMode == "CSS1Compat")
   {
    viewPortHeight = document.documentElement.clientHeight;
    viewPortWidth = document.documentElement.clientWidth;
  
    scrollTop = document.documentElement.scrollTop;
    scrollLeft = document.documentElement.scrollLeft;
   }
  
   var topOffset = Math.ceil(viewPortHeight/2 - element.offsetHeight/2);
   var leftOffset = Math.ceil(viewPortWidth/2 - element.offsetWidth/2);
  
   var top = scrollTop + topOffset - 40;
   var left = scrollLeft + leftOffset - 70;
  
   element.style.position = "absolute";
   element.style.top = top + "px";
   element.style.left = left + "px";
}
 
 
function loadItem(hrefLink) {

  if (xhr) // if created run request 
  {
    xhr.open("GET",hrefLink,true);
    xhr.onreadystatechange = stateChanged;
    xhr.send(null);
  }
}