(function() {
        var imgs = ["btn-services.png", "btn-services-active.png", "btn-portfolio.png", "btn-portfolio-active.png", "btn-contact.png", "btn-contact-active.png"];
        for (var i = 0; i < imgs.length; i++) {
          var img = new Image();
          img.src = PREFIX + "data/site/main/images/" + imgs[i];
        }
      })();