You could try to "weight" certain columns, like this:
<table border="1" style="width: 100%;">
<colgroup>
<col width="80%" />
<col width="20%" />
</colgroup>
<tr>
<td>This cell has more content.</td>
<td>Less content here.</td>
</tr>
</table>
You can also try some more interesting tweaks, like using 0%-width columns and using some combination of the white-space
CSS property.
<table border="1" style="width: 100%;">
<colgroup>
<col width="100%" />
<col width="0%" />
</colgroup>
<tr>
<td>This cell has more content.</td>
<td style="white-space: nowrap;">Less content here.</td>
</tr>
</table>
You get the idea.