<html>
<head>
<script>
function insRow()
{
var x=document.getElementById('myTable').insertRow(0);
var y=x.insertCell(0);
var z=x.insertCell(1);
y.innerHTML="NEW CELL1";
z.innerHTML="NEW CELL2";
}
</script>
</head>
<body>
<table id="myTable" border="1">
<tr>
<td>Row1 cell1</td>
<td>Row1 cell2</td>
</tr>
<tr>
<td>Row2 cell1</td>
<td>Row2 cell2</td>
</tr>
<tr>
<td>Row3 cell1</td>
<td>Row3 cell2</td>
</tr>
</table>
<br>
<input type="button" onclick="insRow()" value="Insert row">
</body>
</html>