jquery移至顶部/底部按钮特效

引入js代码

<script src="jquery-1.3.2.js" type="text/javascript">
</script>
<script src="scroll-startstop.events.jquery.js" type="text/javascript">
</script>
<script>
    $(function() {
        var $elem = $('#content');

        $('#nav_up').fadeIn('slow');
        $('#nav_down').fadeIn('slow');

        $(window).bind('scrollstart',
        function() {
            $('#nav_up,#nav_down').stop().animate({
                'opacity': '0.2'
            });
        });
        $(window).bind('scrollstop',
        function() {
            $('#nav_up,#nav_down').stop().animate({
                'opacity': '1'
            });
        });

        $('#nav_down').click(function(e) {
            $('html, body').animate({
                scrollTop: $elem.height()
            },
            800);
        });
        $('#nav_up').click(function(e) {
            $('html, body').animate({
                scrollTop: '0px'
            },
            800);
        });
    });
</script>