<div id="FloatDIV" style="position: absolute; top: 0px; z-index: 9999; background: #fff000; cursor: pointer;" onclick="window.scrollTo(0,0);">回到顶部</div>

<script type="text/javascript">// <![CDATA[

var MarginLeft = 10;    //浮动层离浏览器右侧的距离

  var MarginTop = document.body.clientHeight - 80;   //浮动层离浏览器顶部的距离(浏览器高度-div高度)

  var Width = 25;            //浮动层宽度

  var Heigth= 80;           //浮动层高度

  //设置浮动层宽、高

  function Set()

  {

      document.getElementById("FloatDIV").style.width = Width + 'px';

      document.getElementById("FloatDIV").style.height = Heigth + 'px';

  }

  //实时设置浮动层的位置

  function Move()

  {

        var b_top = window.pageYOffset

                || document.documentElement.scrollTop

                || document.body.scrollTop

                || 0;

        var b_width= document.body.clientWidth;

      document.getElementById("FloatDIV").style.top = b_top + MarginTop + 'px';

      document.getElementById("FloatDIV").style.left = b_width - Width - MarginLeft + 'px';

      setTimeout("Move();",100);

  }

  Set();

  Move();

// ]]></script>