html - 边框缺少 btn-outline-secondary bootstrap

Question

我在引导程序中遇到 btn-outline-secondary 问题。一旦我将代码上传到我的网站，按钮上的边框就会消失。当我在浏览器中离线查看我的工作 HTML 时，边框是可见的。

我已经尝试过覆盖 boostrap CSS 并增加边框厚度 - 仍然不可见。

包括以下两个代码示例：

一

<div class="row">
 <div class="col-md-4">
  <div class="card mb-4 shadow-sm">
   <img class="card-img-top" src="https:imgur"><img>
  <div class="card-body">
   <h6>Title</h6>
   <p class="card-text">This is a wider card with supporting text below as a natural lead-in to additional content. This content is a little bit longer.</p>
   <a href= "https:..." target="_blank" class="btn btn-outline-secondary" role="button">VIEW</a>
   <div class="d-flex justify-content-between align-items-center">
   </div>
  </div>
 </div>
</div>

二

<div class="container">
 <div class="row">
  <div class="col-sm">
   <button type="button" class="btn btn-outline-secondary" disabled>Text</button>
  </div>
  <div class="col-sm">
   <button type="button" class="btn btn-outline-secondary" disabled>Text</button>
  </div>
  <div class="col-sm">
   <button type="button" class="btn btn-outline-secondary" disabled>Text</button>
  </div>
 </div>
</div>

有什么想法我哪里出错了吗？

标签： htmlcsstwitter-bootstrapbootstrap-4