In CSS 2.1, the effect of 'min-height' and 'max-height' on tables, inline tables, table cells, table rows, and row groups is undefined.
So try wrapping the content in a div, and give the div a min-height
jsFiddle here
<table cellspacing="0" cellpadding="0" border="0" style="width:300px">
<tbody>
<tr>
<td>
<div style="min-height: 100px; background-color: #ccc">
Hello World !
</div>
</td>
<td>
<div style="min-height: 100px; background-color: #f00">
Good Morning !
</div>
</td>
</tr>
</tbody>
</table>