问题是下拉菜单不起作用。我使用Twitter Bootstrap v2.3.2作为前端框架。我用一些来自互联网的开源模式修改了它。请检查下面的长代码以查看潜在的错误。我差点睁眼，寻找我犯的错误。感谢您的慷慨帮助。
<?php
include_once 'admin-class.php';
$admin = new itg_admin();
$admin->_authenticate();
mysql_connect ("localhost", "root","");
$con=mysql_select_db("rfiddb");
if (!$con)
{
die("Could not connect to database.".mysql_error());
}
//$studID=$_POST['studID'];
?>
<!DOCTYPE html>
<html>
<meta charset="utf-8">
<head>
<title>Courses</title>
<!-- Bootstrap -->
<link href="bootstrap/css/bootstrap.min.css" rel="stylesheet" media="screen">
<link href="bootstrap/css/bootstrap-responsive.min.css" rel="stylesheet" media="screen">
<link href="assets/styles.css" rel="stylesheet" media="screen">
<link href="assets/DT_bootstrap.css" rel="stylesheet" media="screen">
<!--[if lte IE 8]><script language="javascript" type="text/javascript" src="vendors/flot/excanvas.min.js"></script><![endif]-->
<!-- HTML5 shim, for IE6-8 support of HTML5 elements -->
<!--[if lt IE 9]>
<script src="http://html5shim.googlecode.com/svn/trunk/html5.js"></script>
<![endif]-->
<script src="vendors/modernizr-2.6.2-respond-1.1.0.min.js"></script>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script>
<script src="bootstrap/js/bootstrap.min.js"></script>
<style type="text/css">
.well { background: #fff; text-align: center; }
.modal { text-align: left; }
</style>
</head>
<body>
<div class="navbar navbar-fixed-top">
<div class="navbar-inner">
<div class="container-fluid">
<a 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>
</a>
<a class="brand" href="#">RFID Attendance Checking System</a>
<div class="nav-collapse collapse">
<ul class="nav pull-right">
<li class="dropdown">
<a href="#" role="button" class="dropdown-toggle" data-toggle="dropdown"> <i class="icon-user"></i> Pangalan <i class="caret"></i>
</a>
<ul class="dropdown-menu">
<li>
<a tabindex="-1" href="#">Profile</a>
</li>
<li class="divider"></li>
<li>
<a tabindex="-1" href="login.html">Logout</a>
</li>
</ul>
</li>
</ul>
<ul class="nav">
<li class="active">
<a href="#">Dashboard</a>
</li>
<li class="dropdown">
<a href="#" data-toggle="dropdown" class="dropdown-toggle">Settings <b class="caret"></b>
</a>
<ul class="dropdown-menu" id="menu1">
<li>
<a href="#">Tools <i class="icon-arrow-right"></i>
</a>
<ul class="dropdown-menu sub-menu">
<li>
<a href="#">Reports</a>
</li>
<li>
<a href="#">Logs</a>
</li>
<li>
<a href="#">Errors</a>
</li>
</ul>
</li>
<li>
<a href="#">SEO Settings</a>
</li>
<li>
<a href="#">Other Link</a>
</li>
<li class="divider"></li>
<li>
<a href="#">Other Link</a>
</li>
<li>
<a href="#">Other Link</a>
</li>
</ul>
</li>
<li class="dropdown">
<a href="#" role="button" class="dropdown-toggle" data-toggle="dropdown">Content <i class="caret"></i>
</a>
<ul class="dropdown-menu">
<li>
<a tabindex="-1" href="#">Blog</a>
</li>
<li>
<a tabindex="-1" href="#">News</a>
</li>
<li>
<a tabindex="-1" href="#">Custom Pages</a>
</li>
<li>
<a tabindex="-1" href="#">Calendar</a>
</li>
<li class="divider"></li>
<li>
<a tabindex="-1" href="#">FAQ</a>
</li>
</ul>
</li>
<li class="dropdown">
<a href="#" role="button" class="dropdown-toggle" data-toggle="dropdown">Users <i class="caret"></i>
</a>
<ul class="dropdown-menu">
<li>
<a tabindex="-1" href="#">User List</a>
</li>
<li>
<a tabindex="-1" href="#">Search</a>
</li>
<li>
<a tabindex="-1" href="#">Permissions</a>
</li>
</ul>
</li>
</ul>
</div>
<!--/.nav-collapse -->
</div>
</div>
</div>
<div class="container-fluid">
<div class="row-fluid">
<div class="span3" id="sidebar">
<ul class="nav nav-list bs-docs-sidenav nav-collapse collapse">
<li>
<a href="index.php"><i class="icon-chevron-right"></i> Dashboard</a>
</li>
<li class="active">
<a href="course.php"><i class="icon-chevron-right"></i> Courses</a>
</li>
<li>
<a href="cys.php"><i class="icon-chevron-right"></i> Courses/Year/Section</a>
</li>
<li>
<a href="sched.php"><i class="icon-chevron-right"></i> Schedules per Section</a>
</li>
<li>
<a href="tables.php"><i class="icon-chevron-right"></i> Records </a>
</li>
<li>
<a href="subjsched.php"><i class="icon-chevron-right"></i> Schedule Codes</a>
</li>
<li>
<a href="subjdesc.php"><i class="icon-chevron-right"></i> Subject Description</a>
</li>
<li>
<a href="#"><span class="badge badge-info pull-right">27</span> Clients</a>
</li>
<li>
<a href="#"><span class="badge badge-info pull-right">1,234</span> Users</a>
</li>
<li>
<a href="#"><span class="badge badge-info pull-right">2,221</span> Messages</a>
</li>
<li>
<a href="#"><span class="badge badge-info pull-right">11</span> Reports</a>
</li>
<li>
<a href="#"><span class="badge badge-important pull-right">83</span> Errors</a>
</li>
<li>
<a href="#"><span class="badge badge-warning pull-right">4,231</span> Logs</a>
</li>
</ul>
</div>
<!--/span-->
<div class="span9" id="content">
<div class="row-fluid">
<!-- block -->
<div class="block">
<div class="navbar navbar-inner block-header">
<div class="muted pull-left">Records</div>
</div>
<div class="block-content collapse in">
<div class="span4">
<div class="table-toolbar">
<div class="btn-group">
<div id="thanks"><p><a data-toggle="modal" href="#form-content"><button class="btn btn-success">Add a New Course<i class="icon-plus icon-white"></i></button/</a></p></div>
</div>
<div class="btn-group pull-right">
<button data-toggle="dropdown" class="btn dropdown-toggle">Tools <span class="caret"></span></button>
<ul class="dropdown-menu">
<li><a href="#">Print</a></li>
<li><a href="#">Save as PDF</a></li>
<li><a href="#">Export to Excel</a></li>
</ul>
</div>
</div>
<form action="nextupdateschedassigned.php" method="POST">
<table cellpadding="0" cellspacing="0" border="0" class="table table-striped table-bordered">
<thead>
<tr>
<th>Course</th>
<th>Delete</th>
</tr>
</thead>
<?php
$resulta = "SELECT Course FROM tblcourse";
$get=mysql_query($resulta);
while($row=mysql_fetch_array($get)){
?>
<tbody>
<tr>
<td class="center"><?php echo $row['Course'] ?></td>
<?php $Course=$row['Course'];?>
<td><?php echo "<a href='deletecourse.php?Course=$Course' class='btn btn-danger'> <i class='icon-remove icon-white'></i>Delete</a>" ?></td>
</tr>
<?php }?>
</tbody>
</table>
</form>
</div>
</div>
</div>
<!-- /block -->
</div>
</div>
</div>
<hr>
<footer>
<p>Copyright © 2014 <a href=http://www.cvsu-rosario.edu.ph/>Cavite State University Rosario Campus</a> • Created by Team RFID</a></p>
</footer>
</div>
<!--/.fluid-container-->
<script src="vendors/jquery-1.9.1.js"></script>
<script src="bootstrap/js/bootstrap.min.js"></script>
<script src="vendors/datatables/js/jquery.dataTables.min.js"></script>
<script src="assets/scripts.js"></script>
<script src="assets/DT_bootstrap.js"></script>
<script>
$(function() {
});
</script>
<!---MODAL-->
<div id="form-content" class="modal hide fade in" style="display: none;">
<div class="modal-header">
<a class="close" data-dismiss="modal">×</a>
<h3>Add a New Course</h3>
</div>
<div class="modal-body">
<form class="span5" id="form_sample_1" class="form-horizontal" action="addcourse.php" method="post">
<div class="alert alert-error hide">
<button class="close" data-dismiss="alert"></button>
You have some form errors. Please check below.
</div>
<div class="alert alert-success hide">
<button class="close" data-dismiss="alert"></button>
Your form validation is successful!
</div>
<div class="control-group">
<label>Course <span class="required">*</span></label>
<div class="controls">
<input type="text" name="Course" pattern="^[a-zA-Z]*$" maxlength="10" value="" class="input-medium" required>
</div>
</div>
Note: Please recheck details after filling in the data.
</div>
<div class="modal-footer">
<input class="btn btn-success" type="submit" value="Save" id="submit">
<a href="#" class="btn" data-dismiss="modal">Cancel</a>
</div>
</form>
</div>
<!---MODAL-->
</body>
</html>