showdown/test/functional/makehtml/cases/features/tables/basic-with-header-ids.html

<table>
    <thead>
        <tr>
            <th id="first_header">First Header</th>
            <th id="second_header">Second Header</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>Row 1 Cell 1</td>
            <td>Row 1 Cell 2</td>
        </tr>
        <tr>
            <td>Row 2 Cell 1</td>
            <td>Row 2 Cell 2</td>
        </tr>
    </tbody>
</table>