<style type="text/css">
.mytable {
    border: 3px solid red;
    width:100%;  
    border-collapse: collapse;
}
.mycell {
    border: 1px solid yellow;
    padding: 5px;
  }
</style>

<table class="mytable">
  <tbody>
    <tr>
      <td class="mycell">test</td>
      <td class="mycell">test</td>
    </tr>
    <tr>
      <td class="mycell">test</td>
      <td class="mycell">test</td>
    </tr>
    <tr>
      <td class="mycell">test</td>
      <td class="mycell">test</td>
    </tr>
  </tbody>
</table>