// Create the request object
  var xml = new XMLHttpRequest();
  
  // Open the asynchronous POST request
  xml.open("POST", "/some/url.cgi", true);
  
  // Set the content-type header, so that the server 
  // knows how to interpret the data that we're sending
  xml.setRequestHeader(
      "Content-Type", "application/x-www-form-urlencoded");
  
  // Make sure the browser sends the right content length of the serialized data –
  // Mozilla-based browsers sometimes have trouble with this
  if ( xml.overrideMimeType )
      xml.setRequestHeader("Connection", "close");
  
  // Establish the connection to the server and send the serialized data
  xml.send( serialize( data ) );