così con annidamento di tabelle :
codice:
<table border="0" width="100%">
  <tr>
    <td width="50%">
      <table border="1" width="100%">
        <tr>
          <td width="100%">tabella 1</td>
        </tr>
        <tr>
          <td width="100%">tabella 1</td>
        </tr>
      </table>
    </td>
    <td width="50%">
      <table border="1" width="100%">
        <tr>
          <td width="100%">tabella 2</td>
        </tr>
        <tr>
          <td width="100%">tabella 2</td>
        </tr>
      </table>
    </td>
  </tr>
</table>