This page shows a difference between IE and Netscape 6 rendering of tables / cells with heights expressed in percentages.
<p>
The table A below has two cells.  Cell A1 contains an invisible image to make the cell fairly tall.  Cell A2 has a height attribute of 100%, and contains another table, table B.
<p>
Table B has two cells, B1 and B2.  B1 has a fixed pixel height of 30 pixels.  B2 has a height of 100%.  In IE, this causes B2 to stretch to fill the entire height of cell A2, while in Netscape 6 / Gecko, it seems to have no impact on the height of cell A2.
<p>
<table border=1 cellpadding=0 cellspacing=0>
<tr>
<td><img src="../images/notfound.gif" HEIGHT=200 WIDTH=10>Cell A1</td>
<td height=100%><table height=100% border=2><tr><td BGDOLOR=#cc00cc HEIGHT=30>Cell B1</td></tr><tr><td bgcolor=#99cc99>Cell B2</td></tr></table></td>
</tr>
</table>