//this is derived from a proof of concept by Stoyan Stefanov, phpied.com

function makeHttpRequest(url, callback_function, return_xml)
{
   var http_request = false;

   if (window.XMLHttpRequest) { // Mozilla/Firefox, Safari, Gecko
       http_request = new XMLHttpRequest();
       if (http_request.overrideMimeType) {
           http_request.overrideMimeType('text/xml');
       }

   } else if (window.ActiveXObject) { // IE
       try {
           http_request = new ActiveXObject("Msxml2.XMLHTTP");
       } catch (e) {
           try {
               http_request = new ActiveXObject("Microsoft.XMLHTTP");
           } catch (e) {}
       }
   }

  //we don't want to display an error message; just a static ad
  if (!http_request) {
      //alert('Sorry, your browser doesn\'t support this feature.');
       return false;
   }
   http_request.onreadystatechange = function() {
 //if request is complete
 if (http_request.readyState == 4) {
  //if status is OK
  if (http_request.status == 200) {
               if (return_xml) {
                   eval(callback_function + '(http_request.responseXML)');
               } else {
                   eval(callback_function + '(http_request.responseText)');
               }
           } else {
  //again, use a static ad
  alert('There was a problem with the request.(Code: ' + http_request.status + ')');
           }
       }
   }
   http_request.open('GET', url, true);
   http_request.send(null);
}

function loadContent(xml)
{

 	var current_ad = xml.getElementsByTagName('content').item(0).firstChild.nodeValue;
    var reload_after = xml.getElementsByTagName('reload').item(0).firstChild.nodeValue;
//this identities id/class name in HTML file
	document.getElementById('adrotate').innerHTML = current_ad;
//if reload value in XML file > 0, we're using a timer to rotate
if (reload_after > 0) {
    try {
        clearTimeout(to);
    } catch (e) {}

    to = setTimeout("nextAd()", parseInt(reload_after));
}

}

function nextAd()
{
    var now = new Date();
    var url = 'rotatecontent.php?ts=' + now.getTime();
    makeHttpRequest(url, 'loadContent', true);
}
//let's load next ad in rotation when page refreshed
window.onload = nextAd;