如下所示,当我的窗口缩小到模拟移动屏幕尺寸时,我的下拉列表变得透明.

navbar http://i44.tinypic.com/rw49p4.png

这是我的代码,这是从引导示例网站复制的,唯一的变化是链接.

<div class="navbar navbar-inverse navbar-fixed-top">
      <div class="container">
        <div class="navbar-header">
          <button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
          </button>
          <a class="navbar-brand" href="#">Project name</a>
        </div>
        <div class="navbar-collapse collapse">
          <ul class="nav navbar-nav">
            <li class="active"><a href="#">Dashboard</a></li>
            <li><a href="#pages">Pages</a></li>
            <li><a href="#extensions">Extensions</a></li>
            <li class="dropdown">
              <a href="#" class="dropdown-toggle" data-toggle="dropdown">Dropdown <b class="caret"></b></a>
              <ul class="dropdown-menu">
                <li><a href="#">Action</a></li>
                <li><a href="#">Another action</a></li>
                <li><a href="#">Something else here</a></li>
                <li class="divider"></li>
                <li class="dropdown-header">Nav header</li>
                <li><a href="#">Separated link</a></li>
                <li><a href="#">One more separated link</a></li>
              </ul>
            </li>
          </ul>
          <div class="navbar-right">
            <p style="color:#fff;">some text</p>
          </div>
        </div><!--/.navbar-collapse -->
      </div>
</div>

[编辑]
我有这个在我的头

<Meta charset="utf-8">
     <Meta name="viewport" content="width=device-width,initial-scale=1.0">
     <Meta name="description" content="">
     <Meta name="author" content="">