Code nút back top

1. Thêm đoạn: <div>  <a class="uptop" href="javascript:scroll(0,0)"> Top </a> sau </div> và trước</body>

2. Thêm Ðoạn:
 .uptop {
    background: url("https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5AtdXISGOFyzerBnyPNhYwNm0GjefniN6DjTwt_yqkM-EvSs8YW3I2YfL09EC_z28RqwddRasz3aZRijRDguaeGm7b3GB0Nv-MEV9ccgfLvxPBJMqRKgTVKNU6CsLwRD4Nvys7S4sH0H_/s1600/up.png") no-repeat scroll -69px top transparent;
    bottom: 10px;
    display: block;
    height: 56px;
    overflow: hidden;
    position: fixed;
    right: 42px;
    text-indent: -999px;
    width: 42px;
}
Vào trước </style> ( trước </head> - See more at: http://longdicaprio.blogspot.com/2013/02/code-nut-back-top.html#sthash.vixLBRpn.dpuf )