smoothscroll.js

<script type="text/javascript">
        $(document).ready(function () {
  
            $(window).scroll(function () {
                if ($(this).scrollTop()) {
                    $('.your-image-class:hidden').stop(true, true).fadeIn();
                }
                else {
                    $('.your-image-class').stop(true, true).fadeOut();
                }
            }); // scroll-to-top

            $(function () {
                $('a[href*=#]:not([href=#])').click(function () {
                    if (location.pathname.replace(/^\//, '') == this.pathname.replace(/^\//, '') && location.hostname == this.hostname) {
                        var target = $(this.hash);
                        target = target.length ? target : $('[name=' + this.hash.slice(1) + ']');
                        if (target.length) {
                            $('html,body').animate({
                                scrollTop: target.offset().top
                            }, 1000);
                            return false;
                        }
                    }
                });
            }); // smooth-scroll
        });
</script>