使用 <dialog> 元素 - 在线编辑器

          < table border = "1" > < tr > < th > January < dialog open > This is an
open dialog window < /dialog></th > < th > February < /th>   <
  th > March < /th></tr > < tr > < td > 31 < /td>  <td>28</td >
  <
  td > 31 < /td></tr > < /table>
        