I keep getting this error when i run this script.

Error reading the response: ReferenceError - Can't find variable: childNodes
I want to return the value of the node <content> but keep getting the error above but assume i am on the right track...?

Thanks

http://www.callsabroad.gb.com/

Code:
function handleServerResponse()
	{
	
		
		var xmlResponse = xmlHttp.responseXML;
		
		//catching potential errors with IE and Opera
		
		if(!xmlResponse || !xmlResponse.documentElement)
		throw("Invalid XML Structure:\n" + xmlHttp.responseText);
		
		//catching potential errors with Firefox
		var rootNodeName = xmlResponse.documentElement.nodeName;
		if(rootNodeName == "parsererror")
		throw("Invalid XML Structure:\n" + xmlHttp.responseText);
		
			
		//obtain the XML documents element
		xmlRoot = xmlResponse.documentElement;
		
		//testing that we received the XML document we expect
		
		if(rootNodeName != "response" || !xmlRoot.firstChild)
		throw("Invalid XML Structure:\n" + xmlHttp.responseText);
		
		
		
		responseText = getNodeValue(xmlRoot.lastChild);
		//display the user message
		
			
			myDiv = document.getElementById("myDivElement");
			myDiv.innerHTML = responseText;
	}
	
	
function getNodeValue(node) {
  var nodeValue = [];
  var i = end = 0;
  var child = null;
  
  if (node.childNodes) {
    end = childNodes.length;
    for (i; i < end; i++) {
      child = node.childNodes[i];
      if (child.nodeName === '#text') {
        nodeValue.push(child.nodeValue);
      }
    }
  } else if (node.nodeValue) {
    nodeValue.push(node.nodeValue);
  }
  
  return nodeValue.join('');
}