JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/css/bootstrap-combined.min.css">
<script src="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/js/bootstrap.min.js"></script>
<div id="navi">
        <div class="container">
          <nav>
            <div class="navbar">
              <div class="navbar-inner">
                <div class="row">
                  <button type="button" class="btn btn-navbar" data-toggle="collapse" data-target=".nav-collapse">
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                  </button>
                  
                  <div class="span2">
                    <a class="brand" href="#"></a>
                  </div>
                    
                  <div class="span10">
                    <div class="nav-collapse collapse">
                      <div class="row">
                        <div class="span8">
                          <ul class="nav">
                            <li class="dropdown">
                              <a href="#" class="dropdown-toggle" data-toggle="dropdown">Lorem 3 opes<b class="caret"></b></i></a>
                              <ul class="dropdown-menu">
                                <li><a href="#">Lorem</a></li>
                                <li><a href="institucional.html">Olosmpa</a></li>
                                <li><a href="#">Lorem 2 isum</a></li>
                                
                              </ul>
                            </li>
                          
                            <li class="dropdown">
                              <a href="#" class="dropdown-toggle" data-toggle="dropdown">Lorem mas<b class="caret"></b></a>
                              <ul class="dropdown-menu">
                                <li><a href="#">Lorem</a></li>
                                <li><a...

CSS

.nav .dropdown.open .caret{
    border-top: none;
    border-bottom: 4px solid #000000;
}