请教javascript中取得对象绝对位置(left, top)的问题.

用offsetLeft和offsetTop取得一个节点的绝对位置的时候, 如果父节的位置如果是设置position: relative;并且设置了margin和padding的宽度(比如都是1em), 这样得到的结果就不正确(IE不正确), 有什么办法可以解决?下面是测试代码:<html>
    <head>
        <title>Test</title>
        <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
        <script type="text/javascript">
            function getPosition(obj){
                var topValue = 0, leftValue = 0;
                while (obj) {
                    leftValue += obj.offsetLeft;
                    topValue += obj.offsetTop;
                    obj = obj.offsetParent;
                }
                return {
                    left: leftValue,
                    top: topValue
                };
            }
        </script>
        <style type="text/css">
         * {
         border: 0;
margin: 0;
padding: 0;
         }
#div1 {
padding: 50px;
}
            #div2 {
                position: relative;
                margin: 20px;
                padding: 50px;
background: red;
            }
#div3 {
height: 50px;
width: 400px;
background: #ccc;
padding: 20px;
}
            #cursor {
                position: absolute;
                background-color: yellow;
width: 50px;
z-index: 1000;
            }
        </style>
    </head>
    <body>
     <div id="div1">
     <div id="cursor">Cursor</div>
        <div id="div2">
            <br>div2<br><br>
<div id="div3" onClick="moveCursor(this);">div3 - cursor should be moved to here</div>
        </div>
        <script type="text/javascript">
            var cursor = document.getElementById('cursor');
var mainDiv = document.getElementById("div2");
            move(cursor, mainDiv);

            function moveCursor(cell){
                var position = getPosition(cell);
                cursor.style.top = position.top + "px";
                cursor.style.left = position.left + "px";
            }
        </script>
</div>
    </body>
</html>