怎么用CSS代码将一个Table的所有线条变为虚线

<style type="text/css">
        table { border-color:Black; border-style:dotted; border-width:0px; border-right-width:1px; border-bottom-width:1px; margin:0; padding:0; border-spacing:0; }
        td { border-color:Black; border-style:dotted; border-width:0px; border-top-width:1px; border-left-width:1px; padding:0; }
    </style>

    <table style=" width:50%; height:100%; ">
        <tr>
            <td>
                 </td>
            <td>
                 </td>
        </tr>
        <tr>
            <td>
                 </td>
            <td>
                 </td>
        </tr>
    </table>