Bootstrap 折叠按钮折叠；但不可见

Question

大家好，我第一次将引导程序用于响应式导航。我查找了几个类似问题的答案，但似乎无法显示我的导航切换按钮。

按钮正确切换并显示我的导航；但是是看不见的。任何见解将不胜感激！ :)

 <!-- NAVIGATION -->
<div class="nav-container">
  <div class"navbar navbar-default" role="navigation">
    <div class="container inner-container">
      <div class="navbar-header">
        <a href="index.php" class="navbar-brand"><img src="img/index/skytek-logo/Skytek_c1_S.png" width="160px" height="90px" alt="Skytek Logo"></a><p class="navbar-slogan">Engineering Excellence</p>
        <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#navHeaderCollapse">
          <span class="sr-only">Toggle navigation</span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
        </button>
      </div>
        <div class="collapse navbar-collapse" id="navHeaderCollapse">
            <ul class="nav navbar-nav navbar-right">
               <li class="active"><a href="index.php">Home</a></li>
               <li><a href="about.php">About Us</a></li>
               <li><a href="#">Support &amp; Services</a></li>
               <li><a href="#">Sales</a></li>
               <li><a href="#">News</a></li>
               <li><a href="#">Contact</a></li>
               <li><a href="#">Careers</a></li>
               <li><a href="#">Login</a></li>
               <li class="search-bar">
                 <form class="navbar-form" role="form" method="get" action="#">
                   <div class="form-group">
                    <input type="text" placeholder="Search" class="form-control">
                   </div>
                   <button type="submit" class="btn btn-success">Go</button>
                 </form>
               </li>
            </ul>  
        </div>
      </div>
    </div>
  </div>
<!-- END NAVIGATION -->

Answer 1

这里缺少等号：

<div class="navbar navbar-default" role="navigation">
----------^

Demo