
This is because of the nested table spellDetailsTable which has a min-width of 670px. For some reason Opera is not applying this min-width to the containing <td>. The quick fix is to add a style="min-width: 690px" to the containing <td>.
However, you seem to have tried to create a fluid layout for some reason, so I can see this method failing as soon as spellDetailsTable grows beyond its minimum. The longterm solution would be to refactor this into floated divs.