js获取页面元素位置函数（浏览器兼容）

 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>a</title>
<script>
function getElementPos(elementId) {
var ua = navigator.userAgent.toLowerCase();
var isOpera = (ua.indexOf('opera') != -1);
var isIE = (ua.indexOf('msie') != -1 && !isOpera); // not opera spoof
var el = document.getElementById(elementId);
if(el.parentNode === null || el.style.display == 'none') {
   return false;
}    
var parent = null;
var pos = [];   
var box;   
if(el.getBoundingClientRect)    //IE
{       
   box = el.getBoundingClientRect();
   var scrollTop = Math.max(document.documentElement.scrollTop, document.body.scrollTop);
   var scrollLeft = Math.max(document.documentElement.scrollLeft, document.body.scrollLeft);
   return {x:box.left + scrollLeft, y:box.top + scrollTop};
}else if(document.getBoxObjectFor)    // gecko  
{
   box = document.getBoxObjectFor(el);
   var borderLeft = (el.style.borderLeftWidth)?parseInt(el.style.borderLeftWidth):0;
   var borderTop = (el.style.borderTopWidth)?parseInt(el.style.borderTopWidth):0;
   pos = [box.x - borderLeft, box.y - borderTop];
} else    // safari & opera  
{
   pos = [el.offsetLeft, el.offsetTop];
   parent = el.offsetParent;   
   if (parent != el) {
    while (parent) {
   pos[0] += parent.offsetLeft;
   pos[1] += parent.offsetTop;
   parent = parent.offsetParent;
    }
   } 
   if (ua.indexOf('opera') != -1 || ( ua.indexOf('safari') != -1 && el.style.position == 'absolute' )) {
    pos[0] -= document.body.offsetLeft;
    pos[1] -= document.body.offsetTop;       
   }  
}            
if (el.parentNode) {
   parent = el.parentNode;
    } else {
   parent = null;
    }
while (parent && parent.tagName != 'BODY' && parent.tagName != 'HTML') { // account for any scrolled ancestors
   pos[0] -= parent.scrollLeft;
   pos[1] -= parent.scrollTop;
   if (parent.parentNode) {
    parent = parent.parentNode;
   } else {
    parent = null;
   }
}
return {x:pos[0], y:pos[1]};
}

function get(divId)
{
   var pos=getElementPos(divId);
   alert("距左边距离"+ pos.x +",距上边距离"+pos.y);

}

</script>
</head>

<body>
<table width="100%"><tr>
   <td><a href="#" id="ccc">aaaa</a></td>
   <td><input type="button" onClick="get('ccc');" value="获取坐标"> </td>
   <td><div id="bbbb" style="background-color:#CCCCCC">层2</div></td>
</tr></table>
<table width="100%"><tr>
   <td>aaaa</td>
   <td><input type="button" onClick="get('aaa');" value="获取坐标"> </td>
   <td><div id="aaa" style="background-color:#CCCCCC">层1</div></td>
</tr></table>
</body>
</html>