关于td变色问题

Question

    <table style="width: 382px">
        <tr>
            <td style="width: 137px">
            </td>
        </tr>
        <tr>
            <td style="width: 137px">
                <a href="#" onmousemove="document.getElementById('td').style.backgroundColor='#ff0';" onmouseout="document.getElementById('td').style.backgroundColor='#fff';"> aaaaaaaa</a></td>
        </tr>
        <tr>
            <td id="td" style="width: 137px; height: 63px;">
            </td>
        </tr>
    </table>