How can I give a table that is inside of a TD 100% height i.e full height of the TD

Question

This is how my table looks like. When I try to give the table 100% height but it doesn't work.

I want the TD that contains "xxx" to have 100% height i.e. the height of the parent TD.

</tr>

    <tr align="left">
        <td valign="top">
            <table style="height:100%" border="1">
                <tr>
                    <td>
                        <span title="Toggle between full screen and frames." id="showHideText"  onclick="showHideFrames();" 
                                class="buttonLabel" style="cursor:pointer; font-size:65%; font-weight:bold;">
                            Hide Frames
                        </span>
                    </td>
                </tr>
                <tr>
                    <td align="bottom" >
                        xxx
                    </td>
                </tr>
            </table>

        </td>