title: bootstrap remove upward arrow in dropdown
body: <p>I am using Twitter bootstap and wish to remove the upward arrow on the dropdown-menu whis is in my nav. I cannot find a reference in the bootstrap.css.</p>
  
  <p><img src="https://i.stack.imgur.com/63dE8.png" alt="Bootstrap"></p>
  
  <pre><code>.navbar .dropdown-menu:after {
   content: '';
   display: inline-block;
   border-left: 6px solid transparent;
   border-right: 6px solid transparent;
   border-bottom: 6px solid #000; /* change color here, modified for a black arrow */
   position: absolute;
   top: -6px;
   left: 10px;
  }
  </code></pre>