右侧部分遮盖左侧 是什么原因
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>某管理系统</title>
<link href="https://netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css" rel="stylesheet">
<!--[if lt IE 9]>
<script src="js/html5shiv.js"></script>
<script src="js/respond.min.js"></script>
<![endif]-->
<style>
body{
padding:50px 0;
overflow: hidden;
}
.sidebar{
background-color: #ddd;
position: fixed;
top: 50px;
left: 0;
bottom: 0;
padding: 20px;
}
.sidebar ul{
margin-left: -20px;
margin-right: -20px;
}
.sidebar .active a,.sidebar .active a:hover,.sidebar .active a:focus{
color: #fff;
background-color: #428bca;
}
</style>
</head>
<body>
<!-- nav -->
<nav class="navbar navbar-inverse navbar-fixed-top" role="navigation">
<div class="content-fluid">
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a href="#" class="navbar-brand">某管理系统</a>
</div>
<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
<ul class="nav navbar-nav">
<li class="active"><a href="#">首页</a></li>
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">功能 <span class="caret"></span></a>
<ul class="dropdown-menu">
<li><a href="#">功能</a></li>
<li><a href="#">功能</a></li>
<li><a href="#">功能</a></li>
<li class="divider"></li>
<li><a href="#">功能</a></li>
<li><a href="#">功能</a></li>
</ul>
</li>
<li><a href="#">帮助</a></li>
</ul>
<form class="navbar-form navbar-right" role="search">
<div class="form-group">
<input type="text" class="form-control" placeholder="用户名...">
<input type="text" class="form-control" placeholder="密码...">
</div>
<button class="btn btn-default">登陆</button>
</form>
</div>
</div>
</nav>
<!-- content -->
<div class="content-fluid">
<div class="row">
<div class="col-md-2 sidebar">
<ul class="nav">
<li class="active"><a href="#">首页</a></li>
<li><a href="#">信息建立</a></li>
<li><a href="#">信息查询</a></li>
<li><a href="#">信息管理</a></li>
<li><a href="#">设置</a></li>
<li><a href="#">帮助</a></li>
</ul>
</div>
<div class="col-md-10 col-md-offset-2" style="background:red">
<h1>管理控制台</h1>
</div>
</div>
</div>
<script src="http://cdn.bootcss.com/jquery/1.11.1/jquery.min.js"></script>
<script src="http://cdn.bootcss.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>
</body>
</html>
