<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
function boom()
{
var tbody = document.getElementById("tbody");
var trX = document.createElement('tr');
tbody.insertBefore(trX, tbody.getElementsByTagName("tr")[0]);
var trY = document.createElement('tr');
tbody.insertBefore(trY, trX);
var tdY1 = document.createElement('td');
tdY1.setAttribute('rowspan', 0);
trY.appendChild(tdY1);
}
</script>
<style>
td {width: 30px; height: 30px;}
</style>
</head>
<body onload="boom();">
<table border cellspacing="10px" cellpadding="10px">
<tbody id="tbody">
<tr>
<td></td>
</tr>
</tbody>
</table>
</body>
</html>