Overflow by %?

[Illasera]

Am trying to make a vertical scrollbar within a table divisionhowever the table height is 100% and the overflow doesn`t seems to like it,When i work with fixed pixels it`s all good.Working

<table class="full_table"> // Width and height = 100% border = 5 and cellpadding & spacing = 0<tr> <td valign="top" align="right" style="direction:rtl; text-align:right;"><div style="overflow:auto; height:355px; >// Spam with text so it will overload</div></td></tr></table>

Not working

<table height="100" width="100"><tr><td valign="top" align="right" style="direction:rtl; text-align:right;"><div style="overflow:auto; height:100%; >// Spam with text so it will overload</div></td></tr></table></table>