<script>
$(window).scroll(function(e) {
                var scrolled = $(window).scrollTop(),
                    header = $('.site-header');

                header.css('top', -(scrolled) * 0.5 + 'px');

                if (scrolled > $(document).height() - $(window).height() - 470) {
                    var scrollPos = scrolled - ($(document).height() - $(window).height() - 470);
                    var position = scrollPos / 10;
                    var opacity = (scrollPos * 1) / 470;
                }
            });
</script>