[jQuery] Method addClass is not working with MS Internet Explorer (IE) 6

[Mindjoy]

I am using onclick event on input type="button" to addClass, but there
is no effect in IE 6, while it works fine in Mozilla and Opera
browsers. I know that IE works fine with such CSS styles, since it
works with my simple code without jQuery (document.getElementById('add-
new-rows').className='display-table-row-group';). Please investigate.

Here is the code:

<form>
  <input type="button" name="my-button" value="Add Something"
onclick="$('#add-new-rows').addClass('display-table-row-group');"/>
</form>
...
<table>
  <tbody id="add-new-rows" class="no-display">
    <tr class="display-table-row-group">
      <td>Something</td>
    </tr>
  </tbody>
</table>

CSS:
.no-display
  {
  display: none;
  }
.display-table-row-group
  {
  display: table-row-group;
  }