tables/mozilla/core/col_widths_auto_per.html

auto table - % width single cell has no effect (not so in IE5)
<table cellspacing=10 border>
 <tr>
  <td width=10%>10% 10%</td></tr>
</table>
<BR>
auto table - % width cell increases table width based on % cell which makes it largest.
Nav4.x does not increase the table too much if the only cells are % 
<table cellspacing=10 border>
 <tr>
  <td width=1%>1%</td>
  <td width=10%>10%</td></tr>
</table>
<BR>