<div id="gotop" onclick="javascript:scroll(0,0);"><img src="data:images/top33x33.png"></div>

<style type="text/css">

#gotop{display:none;position:fixed;right:5px;bottom:4rem;width:33px;height:33px;z-index:999;}

</style>

<script type="text/javascript" src="http://cdn.bootcss.com/jquery/1.11.3/jquery.min.js"></script>

<script type="text/javascript">

$(function(){

    $(window).scroll(function() {//滚屏

        var scrollTop = $(document.body).scrollTop();//滚动高度

        var windowH = $(window).height();//页面高度

        if(scrollTop>windowH){

            $("#gotop").show();

        }else{

            $("#gotop").hide();

        }

    });

});

</script>

var scrollTop = $(this).offset().top;

$(document.body).scrollTop(scrollTop-50);

$('.sidebarnav .sbnl-gotop').click(function(){//回到顶部

    $(document.body).animate({scrollTop: '0px'}, 800);

});

/* 侧导航 */

$(window).scroll(function() {//滚屏

    var scrollTop = $(document.body).scrollTop();//滚动高度

    //var windowH = $(window).height();//页面高度

    if(scrollTop>100){

        $('.sidebarnav').show();

    }else{

        $('.sidebarnav').hide();

    }

});