function randomString() {
	var chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz";
	var string_length = 8;
	var randomstring = '';
	for (var i=0; i<string_length; i++) {
		var rnum = Math.floor(Math.random() * chars.length);
		randomstring += chars.substring(rnum,rnum+1);
	}
	return randomstring;
}

function ajax(url, vars, callbackFunction){
  /* Based on example function from http://en.wikipedia.org/wiki/XMLHttpRequest */
  
  url = url+"?junk="+randomString();
  
  var request = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("MSXML2.XMLHTTP.3.0");
  
  request.open("POST", url, true);
  request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); 
  
  request.onreadystatechange = function(){
  
    if (request.readyState == 4 && request.status == 200) {
  
      if (request.responseText){
  
        callbackFunction(request.responseText);
      }
    }
  }
  request.send(vars);
        
}