I have a table.
For example:
<table>
<tr>
<td>apple</td>
<td>big</td>
</tr>
<tr>
<td>pickle</td>
<td>small</td>
</tr>
</table>
after some fancy jQuery…
<table>
<tr>
<td>apple</td>
<td>big</td>
<td>10kg ------ Is this nice to do, any potential issues?</td>
</tr>
<tr>
<td>pickle</td>
<td>small</td>
</tr>
</table>
Just for fun: http://jsfiddle.net/Czcby/
You will end up with three cells on the first row and two on the second row.
This will not normally display, but if your styling has margins/border/padding on table cells, it can effect the display and layout of the table.