Uuups, what happened here? Aaah, typing error (oll instead of ol). One more try:

1. Kangaroo
2. Possum
3. Koala
4. Alison
5. Rolf Harris
6. Dame Edna

And a hint: future versions of HTML (like the already existing XHTML will require lowercase in HTML and closing of elements, so your list should then look like (hope the example shows up correctly):

  <ol>
      <li>Kangaroo</li>
      <li>Possum</li>
      <li>...</li>
  </ol>