octopress添加回到顶部按钮

<!--返回顶部开始-->
<div id="full" style="width:0px; height:0px; position:fixed; right:80px; bottom:80px; z-index:100; text-align:center; 
background-color:transparent; cursor:pointer;">
    <a href="#" onclick="goTop();return false;"><img src="/images/top.png" border=0 alt="返回顶部"></a> 
</div> 
<script src="/javascripts/top.js" type="text/javascript"></script> <!--返回顶部结束--> 

/**
 * 回到页面顶部
 * @param acceleration 加速度
 * @param time 时间间隔 (毫秒)
 **/
function goTop(acceleration, time) {
      acceleration = acceleration || 0.1;
      time = time || 16;
 
      var x1 = 0;
      var y1 = 0;
      var x2 = 0;
      var y2 = 0;
      var x3 = 0;
      var y3 = 0;
 
      if (document.documentElement) {
            x1 = document.documentElement.scrollLeft || 0;
            y1 = document.documentElement.scrollTop || 0;
      }
      if (document.body) {
            x2 = document.body.scrollLeft || 0;
            y2 = document.body.scrollTop || 0;
      }
      var x3 = window.scrollX || 0;
      var y3 = window.scrollY || 0;
 
      // 滚动条到页面顶部的水平距离
      var x = Math.max(x1, Math.max(x2, x3));
      // 滚动条到页面顶部的垂直距离
      var y = Math.max(y1, Math.max(y2, y3));
 
      // 滚动距离 = 目前距离 / 速度, 因为距离原来越小, 速度是大于 1 的数, 所以滚动距离会越来越小
      var speed = 1 + acceleration;
      window.scrollTo(Math.floor(x / speed), Math.floor(y / speed));
 
      // 如果距离不为零, 继续调用迭代本函数
      if(x > 0 || y > 0) {
            var invokeFunction = "goTop(" + acceleration + ", " + time + ")";
            window.setTimeout(invokeFunction, time);
      }
}