with 5 columns and colspan
, this is possible (click here) (but doesn't make much sense to me):
<table width="100%" border="1" bgcolor="#ffffff">
<colgroup>
<col width="25%">
<col width="25%">
<col width="25%">
<col width="5%">
<col width="20%">
</colgroup>
<tr>
<td>25</td>
<td colspan="2">50</td>
<td colspan="2">25</td>
</tr>
<tr>
<td colspan="2">50</td>
<td colspan="2">30</td>
<td>20</td>
</tr>
</table>