<!DOCTYPE html>
<html style="font-family: Ahem; font-size: 50px; -webkit-font-smoothing: none;">
<body>
<script>
document.body.offsetTop;
test = document.createElement('div');
document.body.appendChild(test)
test.appendChild(document.createElement('tr'));
tr = document.createElement('tr');
test.appendChild(tr);
document.body.offsetTop;
test.insertBefore(document.createElement('div'), tr);
</script>
</body>
</html>