【position】
<!DOCTYPE html>
<html>
<head>
<script type='text/javascript'>
window.onload=function(){
var elem = document.getElementById('elem');
console.log('top = ' + elem.offsetTop + '\nleft = ' + elem.offsetLeft);
}
</script>
</head>
<body>
<br /> asdda
<span id="elem">me</span>
</body>
</html>
