(function($) {
  var cache = [];
  // Arguments are image paths relative to the current page.
  $.preLoadImages = function() {
    var args_len = arguments.length;
    for (var i = args_len; i--;) {
      var cacheImage = document.createElement('img');
      cacheImage.src = arguments[i];
      cache.push(cacheImage);
    }
  }
})(jQuery)

jQuery.preLoadImages("images/menu_01_on.jpg","images/menu_01_off.jpg","images/menu_02_on.jpg","images/menu_02_off.jpg","images/menu_03_on.jpg","images/menu_03_off.jpg","images/menu_04_on.jpg","images/menu_04_off.jpg","images/menu_05_on.jpg","images/menu_05_off.jpg","images/menu_06_on.jpg","images/menu_06_off.jpg","images/menu_07_on.jpg","images/menu_07_off.jpg");