看看这个例子,不存在定位问题
<div align=center>
<span id="pad1" onClick="pop()">pad1</span>|
<span id="pad2" onClick="pop()">pad2</span>|
<span id="pad3" onClick="pop()">pad3</span>|
<span id="pad4" onClick="pop()">pad4</span>|
</div>
<span id="popup" style="position:absolute;display:none" onMouseOut="this.style.display='none'"></span><script>
function pop() {
  el = event.srcElement;
  switch(el.id) {
    case "pad1":
      popup.innerHTML = "弹出菜单一<br>请选择<br>移出关闭";
      break;
    case "pad2":
      popup.innerHTML = "弹出菜单二<br>请选择<br>移出关闭";
      break;
    case "pad3":
      popup.innerHTML = "弹出菜单三<br>请选择<br>移出关闭";
      break;
    case "pad4":
      popup.innerHTML = "弹出菜单四<br>请选择<br>移出关闭";
      break;
  }
  popup.style.left = el.offsetLeft;
  popup.style.display = "block";
}
</script>