<style>
  table {
    border-collapse: collapse;
    width: 100%;
  }
  th, td {
    border: 1px solid black;
    padding: 8px;
    text-align: left;
  }
</style>

<table>
 <tr>
      <td colspan="2">Header Cell</td>
  </tr>
 <tr>
     <td>Row 1, Cell 1</td>
     <td>Row 1, Cell 2</td>
 </tr>
 <tr>
     <td rowspan="2">Row 2, Cell 1</td>
     <td>Row 2, Cell 2</td>
 </tr>
 <tr>
  <td>Row 3, Cell 2</td>
 </tr>
</table>