Tracking function.

trackme.js

 _doTracking: function(tag){
    var cacheBuster = (new Date()).getTime(),
        $body = $('body'),
        $tracker = $('#dynamic-tracking');
        tag += "&cb=$timestamp$";
    // Select or create tracking image
    if( $tracker.length > 0 ) {
      // Updated existing element
      $tracker.attr('src', tag.replace(/\$timestamp\$/, cacheBuster));
    } else {
      // Create new img tag in page
      $tracker = $('<img/>');
      $tracker.attr('id', "dynamic-tracking");
      $tracker.attr('src', tag.replace(/\$timestamp\$/, cacheBuster));
      $tracker.css({"display":"none"});
      $body.append($tracker);
    }
  }