you can wrap the content of the <tbody>
in a scrollable <div>
:
html
....
<tbody>
<tr>
<td colspan="2">
<div class="scrollit">
<table>
<tr>
<td>January</td>
<td>$100</td>
</tr>
<tr>
<td>February</td>
<td>$80</td>
</tr>
<tr>
<td>January</td>
<td>$100</td>
</tr>
<tr>
<td>February</td>
<td>$80</td>
</tr>
...
css
.scrollit {
overflow:scroll;
height:100px;
}
see my jsfiddle, forked from yours: http://jsfiddle.net/VTNax/2/