// JavaScript Document
// threadsafe asynchronous XMLHTTPRequest code
function ajaxSend(url, callback){


	// we use a javascript feature here called "inner functions"
	// using these means the local variables retain their values after the outer function
	// has returned. this is useful for thread safety, so
	// reassigning the onreadystatechange function doesn't stomp over earlier requests.


	function ajaxBindCallback(){
		if (ajaxRequest.readyState == 4) {
			if (ajaxRequest.status == 200) {
				if (ajaxCallback){
					ajaxCallback(ajaxRequest.responseText);
				} else {
					alert('no callback defined');
				}
			} else {
				ajaxCallback("There was a problem retrieving the xml data:\n" + ajaxRequest.status + ":\t" + ajaxRequest.statusText + "\n" + ajaxRequest.responseText);
			}
		}
	}


	// use a local variable to hold our request and callback until the inner function is called...
	var ajaxRequest = null;
	var ajaxCallback = callback;
	
	
	// bind our callback then hit the server...
	if (window.XMLHttpRequest) {
		// moz et al
		ajaxRequest = new XMLHttpRequest();
		ajaxRequest.onreadystatechange = ajaxBindCallback;
		ajaxRequest.open("GET", url, true);
		ajaxRequest.send(null);
	} else if (window.ActiveXObject) {
		// ie
		ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
		if (ajaxRequest) {
			ajaxRequest.onreadystatechange = ajaxBindCallback;
			ajaxRequest.open("GET", url, true);
			ajaxRequest.send();
		}
	}
}