This illustrates a table layout bug which presents in a number of browsers. To the right you'll see how the table renders in various browsers. Here's the table in your browser:
| Spanning header | Third column | Fourth column | |
| Indented entry | Fourth column | ||
Here's the markup for the table:
<table border=1>
<tr>
<td colspan=2 nowrap>Spanning header</td>
<td>Third column</td>
<td>Fourth column</td>
</tr>
<tr>
<td width=25> </td>
<td colspan=2>Indented entry</td>
<td>Fourth column</td>
</tr>
</table>