td>.mx-auto</td> <td>margin: 0 auto</td></tr></tbody></table> <div class="language-html extra-class"><pre class="language-html"><code>  <span class="token comment">&lt;!-- 默认值： --&gt;</span>
  <span class="token comment">&lt;!-- m-1 = margin: 5px --&gt;</span>
  <span class="token comment">&lt;!-- m-2 = margin: 10px --&gt;</span>
  <span class="token comment">&lt;!-- m-3 = margin: 15px --&gt;</span>
  <span class="token comment">&lt;!-- ... --&gt;</span>
  <span class="token comment">&lt;!-- m-20 = 