width in table

Hi,

Maybe this is a simple question, but I can't seem to get it to work.
Let's say I have this table:

        <table style="width: 300px">
            <tr>
                <th>Header</th>
                <td>1</td>
                <td>22</td>
                <td>333</td>
            </tr>
        </table>

How can I use CSS 2 to make the th take minimal width and let the other 
columns divide the rest of width equally. Also I do not know how many 
data columns I have.