警告框中的链接

用 .alert-link 工具类，可以为链接设置与当前警告框相符的颜色。

<div class="alert alert-success" role="alert">
  <a href="#" class="alert-link">...</a>
</div>
<div class="alert alert-info" role="alert">
  <a href="#" class="alert-link">...</a>
</div>
<div class="alert alert-warning" role="alert">
  <a href="#" class="alert-link">...</a>
</div>
<div class="alert alert-danger" role="alert">
  <a href="#" class="alert-link">...</a>
</div>