CSS 页面顶部阴影和给浏览器强制加上滚动条

 /*给浏览器强制加上滚动条*/
        html{height: 101%;}
        /*页面顶部阴影*/
        body:before{
            content: "";
            position: fixed;
            top:-10px;
            left:0;
            width:100%;
            height:10px;
            -webkit-box-shadow: 0px 0px 10px rgba(0,0,0,.8);
            -moz-box-shadow: 0px 0px 10px rgba(0,0,0,.8);
            box-shadow: 0px 0px 10px rgba(0,0,0,.8);
            z-index: 100;
        }