HN does something similar. When you up/down vote something, it creates a new js Image object and sets the src to the HN site, which then pings the server. No need for ajax.<p>&#60;code&#62;
  var score = byId('score_' + item);
  var newscore = parseInt(score.innerHTML) + (v[0] == 'up' ? 1 : -1);
  score.innerHTML = newscore + (newscore == 1 ? ' point' : ' points');<p><pre><code>  // hide arrows
  byId('up_'   + item).style.visibility = 'hidden';
  byId('down_' + item).style.visibility = 'hidden';

  // ping server
  var ping = new Image();
  ping.src = node.href;</code></pre>
&#60;/code&#62;