<html>
<head>
<script type="text/javascript">
function showEmptyCells()
{
document.getElementById('myTable').style.emptyCells="show";
}
</script>
</head>
<body>
<table border="1" id="myTable">
<tr>
<td>100</td>
<td>200</td>
</tr>
<td>300</td>
<td></td>
</table>
<input type="button" onclick="showEmptyCells()" value="Show empty cells">
</body>
</html>