nested table missing end td.
<br>Nav. 4.0(bug): For inner table td does NOT terminate previous td.
<br>Xena 6.0: end td is always optional.

<table border>
  <caption> caption of table1.</caption>
  <tr>
    <td>cell 1-1
    <td>cell 1-2
  <tr>
    <td>cell 1-3
    <td>cell 1-4
       <table border>
       <caption> caption of table2.</caption>
       <tr>
           <td>cell1 in table2
           <td>cell2 in table2
       <tr>
           <td>cell3 in table2
           <td>cell4 in table2
       </table>
</table>
<br> Last text.