var http_request = false;
var xmldoc;
var textdoc;
var functionToCall;

function makeRequest(url, parameters, f) {
  http_request = false;
  if (window.XMLHttpRequest) {
    http_request = new XMLHttpRequest();
    if (http_request.overrideMimeType) { http_request.overrideMimeType('text/xml'); }
  } else if (window.ActiveXObject) {
    try { http_request = new ActiveXObject("Msxml2.XMLHTTP"); } 
    catch (e) {
      try { http_request = new ActiveXObject("Microsoft.XMLHTTP"); } 
      catch (e) {}
    }
  }

  if (!http_request) {
    return false;
  }
 
  functionToCall = f;
  http_request.onreadystatechange = alertContents;
  http_request.open('POST', url, true);
  http_request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
  http_request.setRequestHeader("Content-length", "parameters.length");
  http_request.setRequestHeader("Connection", "close");
  http_request.send(parameters);
}

function alertContents() {
  if (http_request.readyState == 1 ) {
  }
  if (http_request.readyState == 2 ) {
  }
  if (http_request.readyState == 3 ) {
  }
  if (http_request.readyState == 4 ) {
    if (http_request.status == 200) {
      textdoc = http_request.responseText;
      xmldoc  = http_request.responseXML;
      eval(functionToCall + '()');
    }
  }
}