function makePOSTRequest (url, string) {
	var ajaxRequest = new Ajax.Request(
    url,{method: 'post', parameters: string, onComplete: handleResponse});
}

function handleResponse(http_request) {
	if (http_request.readyState == 4) {
         if (http_request.status == 200) {
            result = http_request.responseText;
            $('displayResponse').innerHTML = result;            
         } else {
            alert('There was a problem with the request.');
         }
      }
}