Try this instead.
<table style="width: 100%">
<tr>
<th style="width: 20%">
column 1
</th>
<th style="width: 40%">
column 2
</th>
<th style="width: 40%">
column 3
</th>
</tr>
<tr>
<td style="width: 20%">
value 1
</td>
<td style="width: 40%">
value 2
</td>
<td style="width: 40%">
value 3
</td>
</tr>
</table>