/**
     * ::::::: Scroll Down
     */
     var $viewportHeight = $(window).height();
     var $target_down = $('#target-down');
     // Download the viewport
     $target_down.click(function(event){
         $('html, body').animate({scrollTop: '+=' + $viewportHeight}, 800);
     });
    $(window).scroll(function() {
        // Check if reach bottom of the page
        if($(window).scrollTop() + $viewportHeight == $(document).height()) {
            $target_down.fadeOut( 500 );
        } else {
            $target_down.fadeIn( 500 );
        }
    });