<html>
<head>
<script>
function rowRules()
{
document.getElementById('myTable').rules="rows";
}
function colRules()
{
document.getElementById('myTable').rules="cols";
}
</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="rowRules()" value="Show only row borders">
<input type="button" onclick="colRules()" value="Show only col borders">
</body>
</html>