为什么我的侧边导航栏设置position：fixed后，右边的内容全部跑到左边来了，怎么解决，我目的是让侧边栏背景颜色跟随页面高度
<!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="http://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{
margin-top:50px;
}
.sidebar{
background-color:#e5e5e5;
position:fixed;
top:51px;
bottom:0px;
}
.sidebar ul{
margin-top:20px;
}
.grid{
margin-top:10px;
}
.progress{
margin-top:10px;}
</style>
</head>
<body>
<nav class="navbar navbar-default navbar-fixed-top navbar-inverse">
<div>
<!-- Brand and toggle get grouped for better mobile display -->
<div>
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#demo-navbar" aria-expanded="false">
<span>Toggle navigation</span>
<span></span>
<span></span>
<span></span>
</button>
<a href="#">某管理系统</a>
</div>
<!-- Collect the nav links, forms, and other content for toggling -->
<div class="collapse navbar-collapse" id="demo-navbar">
<ul class="nav navbar-nav">
<li><a href="#">首页<span>(current)</span></a></li>
<li>
<a href="#" data-toggle="dropdown" >功能<span></span></a>
<ul role="mennu">
<li><a href="#tab-chrome">Chrom</a></li>
<li><a href="#tab-firefox">Firefox</a></li>
<li><a href="#tab-opera">Opera</a></li>
<li><a href="#tab-sarfari">Safari</a></li>
<li><a href="#tab-ie">IE</a></li>
</ul>
</li>
<li><a href="#">帮助</a></li>
</ul>
<form class="navbar-form navbar-right" role="search">
<div>
<input type="text" placeholder="用户名...">
<input type="password" placeholder="密码...">
</div>
<button type="submit" class="btn btn-default">登录</button>
</form>
</div><!-- /.navbar-collapse -->
</div><!-- /.container-fluid -->
</nav>
<div>
<div>
<div class="col-md-3 sidebar">
<ul class="nav nav-pills nav-stacked">
<li role="presentation"><a href="#">首页</a></li>
<li></li>
<li role="presentation"><a href="#">信息建立</a></li>
<li role="presentation"><a href="#">信息查询</a></li>
<li role="presentation"><a href="#">信息管理</a></li>
<li></li>
<li role="presentation"><a href="#">设置</a></li>
<li role="presentation"><a href="#">帮助</a></li>
</ul>
</div><!--侧边栏结束-->
<div>
<h2>管理控制台</h2>
<hr>
<div>
<div>
<button type="button" class="btn btn-default">Default</button>
<!-- Provides extra visual weight and identifies the primary action in a set of buttons -->
<button type="button" class="btn btn-primary">Primary</button>
<!-- Indicates a successful or positive action -->
<button type="button" class="btn btn-success">Success</button>
<!-- Contextual button for informational alert messages -->
<button type="button" class="btn btn-info">Info</button>
<!-- Indicates caution should be taken with this action -->
<button type="button" class="btn btn-warning">Warning</button>
<!-- Indicates a dangerous or potentially negative action -->
<button type="button" class="btn btn-danger">Danger</button>
</div>
</div>
<div class="row grid">
<div>
<div class="panel panel-primary">
<div>最新提醒</div>
<div>
<div class="alert alert-success" role="alert"><strong>提示</strong>您的订单（2014001）已审批通过</div>
<div class="alert alert-warning" role="alert"><strong>提示</strong>您的订单（2014002）在审批通中</div>
<div class="alert alert-danger" role="alert"><strong>提示</strong>您的订单（2013002）未通过</div>
</div>
</div>
</div><!--4栅格结束-->
<div>
<div class="panel panel-primary">
<div>我的任务</div>
<div>
<ul >
<li class="list-group-item list-group-item-success">
<span>24</span>
订单审批
</li></ul>
<ul >
<li class="list-group-item list-group-item-success">
<span>26</span>
收款确认
</li></ul>
<ul >
<li class="list-group-item list-group-item-success">
<span>14</span>
付款确认
</li>
</ul>
</div>
</div>
</div>
</div>
<div class="row grid">
<div>
<div class="panel panel-primary">
<div>最新订单</div>
<div>
<table class="table table-striped">
<thead><tr>
<th>#</th>
<th>产品</th>
<th>数量</th>
<th>总金额</th>
<th>业务员</th>
</tr></thead>
<tbody>
<tr>
<td>1</td>
<td>Apple Macbook Air</td>
<td>10</td>
<td>80000</td>
<td>王小贱</td>
</tr>
<tr>
<td>2</td>
<td>Apple iPad Air</td>
<td>20</td>
<td>65000</td>
<td>尹开花</td>
</tr>
<tr>
<td>3</td>
<td>Apple Macbook pro</td>
<td>5</td>
<td>50000</td>
<td>刘老根</td>
</tr>
</tbody>
</table>
<button type="button" class="btn btn-info">查看详情>></button>
</div>
</div>
</div><!--4栅格结束-->
<div>
<div class="panel panel-primary">
<div>工程进度</div>
<div>
<label class="label label-primary">水井挖掘工程</label>
<div>
<div role="progressbar" aria-valuenow="60" aria-valuemin="0" aria-valuemax="100" style="width: 60%;">
<span>60% Complete</span>
</div>
</div>
<label class="label label-danger">基建工程</label>
<div>
<div class="progress-bar progress-bar-danger" role="progressbar" aria-valuenow="60" aria-valuemin="0" aria-valuemax="100" style="width: 60%;">
<span>60% Complete</span>
</div>
</div>
</div>
</div>
</div>
</div>
</div><!--控制台文字-->
</div><!--sidebar上一层-->
</div><!--最外面-->
<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>
