First of all, your code is wrong.
The bottom row spans over two columns so it should be like this.
Code:
<table width="500">
<tr>
<td>1</td>
<td>2</td>
</tr>
<tr>
<td colspan="2">3</td>
</tr>
</table>
Second... try picking up an HTML manual somewhere? Christ, you've been posting since 2002?!