Question

When I try to use position: relative / position: absolute on a <th> or <td> in Firefox it doesn’t seem to work.

Answer 1

Easy and most proper way would be to wrap the contents of the cell in a div and add position:relative to that div.

example:

<td>
  <div style="position:relative">
      This will be positioned normally
      <div style="position:absolute; top:5px; left:5px;">
           This will be positioned at 5,5 relative to the cell
      </div>
  </div>
</td>