我有一个引导程序下拉菜单（下面列出的代码）工作正常，但有时它会毫无理由地停止工作。任何人都可以检查代码，看看它有什么问题？我一直在使用Google Chrome和Firefox;同样的问题。我也读过关于这个问题的其他问题;但所有关于插件。此代码不使用任何插件。
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8" />
<meta name="viewport" content="width=device-width">
<title>Example</title>
<!-- Jquery plugin -->
<!--<script type='text/javascript' src="/js/jquery-1.11.2.min.js"></script>-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
<!-- Bootstrap plugin -->
<!-- Latest compiled and minified CSS -->
<!--<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">-->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.5/css/bootstrap.css">
<!-- Optional theme -->
<!--<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap-theme.min.css">-->
<!-- Latest compiled and minified JavaScript -->
<!--<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.5/js/bootstrap.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.3.0/css/font-awesome.min.css" type="text/css" rel="stylesheet">
<!-- BOOTSTRAP DATE PICKER -->
<link rel="stylesheet" href="http://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.3.0/css/datepicker.min.css" />
<link rel="stylesheet" href="http://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.3.0/css/datepicker3.min.css" />
<script src="http://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.3.0/js/bootstrap-datepicker.min.js"></script>
<!-- BOOTSTRAP VALIDATOR -->
<script type='text/javascript' src="inc/lib/bootstrapvalidator-master/js/bootstrapValidator.min.js"></script>
<script type='text/javascript' src="inc/lib/bootstrapvalidator-master/js/language/pt_BR.js"></script>
<script type='text/css' src="inc/lib/bootstrapvalidator-master/css/bootstrapValidator.min.css"></script>
<!--
==================================================
NAVBAR
==================================================
-->
<div class="container cima">
<div class="col-sm-12">
<div class="panel panel-default col-centered">
<div class="panel-heading">
<h5>Sistema de Acompanhamento de Concursos e Processos Seletivos</h5>
</div>
<div class="panel-body">
<ul class="nav nav-pills">
<li class="active"><a href="index.php"><i class="icon-home icon-2x"></i>Início<br></a></li>
<li class="dropdown">
<a class="dropdown-toggle" href="#" data-toggle="dropdown">Certame<span class="caret"></span></a>
<ul class="dropdown-menu" role="menu">
<li><a href="./cadastraCertame.php">Cadastra Certame</a></li>
<li><a href="./cadastraValidadeCertame.php">Cadastra Validade do Certame</a></li>
</ul>
</li>
<li class="dropdown">
<a class="dropdown-toggle" href="#" data-toggle="dropdown">Cronograma<b class="caret"></b></a>
<ul class="dropdown-menu" role="menu">
<li><a href="./cadastraEtapaCronograma.php">Cadastra Etapas de Cronograma</a></li>
<li><a href="./cadastraCronograma.php">Cadastra Cronograma</a></li>
</ul>
</li>
<li class="dropdown">
<a class="dropdown-toggle" href="#" data-toggle="dropdown">Homologação<b class="caret"></b></a>
<ul class="dropdown-menu" role="menu">
<li><a href="manutenção.php">Manutenção</a></li>
<li><a href="quem-somos.php">Quem Somos</a></li>
<li><a href="contate-nos.php">Contate-nos</a></li>
</ul>
</li>
</ul>
</div>
</div>
</div>
</div>