html5 thread tag

In a table like below..
<table border="1">
<thead>
<tr>
<th>letter</th>
<th>position</th>
</tr>
</thead>
<tfoot>
<tr>
<td>2</td>
<td>2</td>
</tr>
</tfoot>
<tbody>
<tr>
<td>a</td>
<td>1</td>
</tr>
<tr>
<td>b</td>
<td>2</td>
</tr>
</tbody>
</table>

expect seperately scrollable header/ footer/rows of a table