function makeHttpRequest(url, callback_function, return_xml)
{
  var http_request, response, i;

  var activex_ids = [
    'MSXML2.XMLHTTP.3.0',
    'MSXML2.XMLHTTP',
    'Microsoft.XMLHTTP'
      ];

  if (window.XMLHttpRequest) { // Mozilla, Safari, IE7+...
    http_request = new XMLHttpRequest();
    if (http_request.overrideMimeType) {
      http_request.overrideMimeType('text/xml');
    }
  } else if (window.ActiveXObject) { // IE6 and older
    for (i = 0; i < activex_ids.length; i++) {
      try {
	http_request = new ActiveXObject(activex_ids[i]);
      } catch (e) {}
    }
  }

  if (!http_request) {
    alert('Unfortunately your browser doesn\'t support this feature.');
    return false;
  }

  http_request.onreadystatechange = function() {
    if (http_request.readyState !== 4) {
      // not ready yet
      return;
    }
    if (http_request.status !== 200) {
      // ready, but not OK
      alert('There was a problem with the request.(Code: ' + http_request.status + ')');
      return;
    }
    if (return_xml) {
      response = http_request.responseXML;
    } else {
      response = http_request.responseText;
    }
    // invoke the callback
    callback_function(escape(response));
  };

  http_request.open('GET', url, true);
  http_request.send(null);
}