Mine

var request = false;
var global_content = "";

if (!request && typeof XMLHttpRequest != 'undefined') {
  request = new XMLHttpRequest();
}

function ajaxSwitch(content) {
var url = "addbookmark.php?id=" + escape(content);
request.open("GET", url, true);
global_content = content;
request.onreadystatechange = go;
request.send(null);
}

function go {
  if (request.readyState == 4) {
	  if (request.status == 200) {
		var response = request.responseText;
		document.getElementById("ajax" + global_content).innerHTML = response;
	  }
  }
}