// Preload a few images that are top priority
(function($) {
    var cache = [];
    $.preLoadImages = function() {
      var images = arguments[0];
      for (var i = 0; i < images.length; i++) {
        var cacheImage = document.createElement('img');
        cacheImage.src = images[i];
        cache.push(cacheImage);
      }
    };
  })(jQuery);
  
  $.preLoadImages([
    'images/course1_pic2.png', 'images/course1_pic.png', 'images/course1_pic4.png', 'images/course2_pic4.png', 'images/course1_pic3.png', 'images/course2_pic.png', 'images/course2_pic2.png', 'images/course2_pic3.png'
  ]);