如何获得这个html控件相对与页面的坐标?


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
 <HEAD>
  <TITLE> New Document </TITLE>
  <META NAME="Generator" CONTENT="EditPlus">
  <META NAME="Author" CONTENT="">
  <META NAME="Keywords" CONTENT="">
  <META NAME="Description" CONTENT="">
  <SCRIPT LANGUAGE="JavaScript">
  <!--
function Position(){
var e = document.getElementById("WorkID");
var oTop = e.offsetTop;
var oLeft = e.offsetLeft;
while(e = e.offsetParent){
oTop += e.offsetTop;
oLeft += e.offsetLeft;
}
alert("y="+oTop+"x="+oLeft)
}
  //-->
  </SCRIPT>
 </HEAD>  <body> 
    <form id="form1" runat="server"> 
    <div> 
        <table> 
              <tr > 
                <td > <input id="WorkID" type="text" runat="server" size=10 /> </td> 
                <td > <input id="InventID" type="text"  runat="server" size=20 /> </td> 
              </tr> 
        </table> 
    </div> 
<INPUT TYPE="button" value="获得" onclick="Position()">
    </form> 
</body></HTML>