下面的例子指定了一个表格的Th和TD元素的黑色边框 - 在线编辑器

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <style>
    table,
    th,
    td {
      border: 1px solid black;
    }
  </style>
</head>

<body>
  <table>
    <tr>
      <th>Firstname</th>
      <th>Lastname</th>
    </tr>
    <tr>
      <td>Peter</td>
      <td>Griffin</td>
    </tr>
    <tr>
      <td>Lois</td>
      <td>Griffin</td>
    </tr>
  </table>
</body>
</html>
​x
 
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <style>
    table,
    th,
    td {
      border: 1px solid black;
    }
  </style>
</head>
​
<body>
  <table>
    <tr>
      <th>Firstname</th>
      <th>Lastname</th>
    </tr>
    <tr>
      <td>Peter</td>
      <td>Griffin</td>
    </tr>
    <tr>
      <td>Lois</td>
      <td>Griffin</td>
    </tr>
  </table>
</body>
</html>