// JavaScript Document
var isDOM = (document.getElementById ? true : false);
var isIE4 = ((document.all && !isDOM) ? true : false);
var isNS4 = (document.layers ? true : false);
var isNS = navigator.appName == "Netscape";

function getRef(id) {
  if (isDOM) return document.getElementById(id);
  if (isIE4) return document.all[id];
  if (isNS4) return document.layers[id];
}

function getSty(id) {
  x = getRef(id);
  return (isNS4 ? getRef(id) : getRef(id).style);
}

function moveRightEdge() {
  var yMenuFrom, yMenuTo, yOffset, timeoutNextCheck;

  if (isNS4) {
    yMenuFrom = divMenu.top;
    yMenuTo = windows.pageYOffset + 400;
  } else if (isDOM) {
    yMenuFrom = parseInt (divMenu.style.top, 10);
    yMenuTo = (isNS ? window.pageYOffset : document.documentElement.scrollTop) + document.documentElement.clientHeight - 100;//图标的Ｙ坐标位置
  }

  timeoutNextCheck = 100;

  if (yMenuFrom != yMenuTo) {
    yOffset = Math.ceil(Math.abs(yMenuTo - yMenuFrom) / 20);
    if (yMenuTo < yMenuFrom)
      yOffset = -yOffset;
    if (isNS4)
      divMenu.top += yOffset;
    else if (isDOM)
      divMenu.style.top = parseInt (divMenu.style.top, 10) + yOffset;
      timeoutNextCheck = 10;
  }

  divMenu.style.left = document.documentElement.clientWidth/2+480;//图标的Ｘ坐标位置

  setTimeout ("moveRightEdge()", timeoutNextCheck);
}

var m_loc = location.href;

site_posi="<span id='divMenu' style='position: absolute;visibility:visible'><a href='#' class='other' onfocus='this.blur();'><img src='http://www.znhr.com/project/zn/images/top.gif' border='0' alt='返回顶部'></a></span>";//这里可以采用你自己的图标

  document.write(site_posi);

  if (isNS4) {
    var divMenu = document["divMenu"];
    divMenu.top = top.pageYOffset + 50;
    divMenu.visibility = "visible";
    moveRightEdge();
  } else if (isDOM) {
    var divMenu = getRef('divMenu');
    divMenu.style.top = (isNS ? window.pageYOffset : document.documentElement.scrollTop) + 350;//刚打开页面时，图标的Ｙ坐标位置
    divMenu.style.visibility = "visible";
    moveRightEdge();
  }