(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("img/nav/about-us-over.jpg", "img/nav/coach-education-over.jpg", "img/nav/contact-us-over.jpg", "img/nav/elite-sport-over.jpg", "img/nav/home-over.jpg", "img/nav/training-over.jpg");