<nav class="navbar navbar-default navbar-fixed-top" role="navigation">
      <div class="container">
        <div class="navbar-header">
          <button class="navbar-toggle collapsed" aria-expanded="false" aria-controls="navbar" type="button" data-toggle="collapse" data-target="#navbar">
            <span class="sr-only">Toggle navigation</span>
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
          </button>
          <a class="navbar-brand" href="http://www.mamicode.com/#">Project name</a>
        </div>
        <div class="navbar-collapse collapse" id="navbar">
          <ul class="nav navbar-nav">
            <li class="active"><a href="http://www.mamicode.com/#">Home</a></li>
            <li><a href="http://www.mamicode.com/#about">About</a></li>
            <li><a href="http://www.mamicode.com/#contact">Contact</a></li>
            <li class="dropdown">
              <a class="dropdown-toggle" aria-expanded="false" href="http://www.mamicode.com/#" data-toggle="dropdown">Dropdown <span class="caret"></span></a>
              <ul class="dropdown-menu" role="menu">
                <li><a href="http://www.mamicode.com/#">Action</a></li>
                <li><a href="http://www.mamicode.com/#">Another action</a></li>
                <li><a href="http://www.mamicode.com/#">Something else here</a></li>
                <li class="divider"></li>
                <li class="dropdown-header">Nav header</li>
                <li><a href="http://www.mamicode.com/#">Separated link</a></li>
                <li><a href="http://www.mamicode.com/#">One more separated link</a></li>
              </ul>
            </li>
          </ul>
          <ul class="nav navbar-nav navbar-right">
            <li><a href="http://www.mamicode.com/navbar/">Default</a></li>
            <li><a href="http://www.mamicode.com/navbar-static-top/">Static top</a></li>
            <li class="active"><a href="http://www.mamicode.com/">Fixed top</a></li>
          </ul>
        </div><!--/.nav-collapse -->
      </div>
    </nav>

Bootstrap——导航栏编写