但复制了老师的那行代码也不行：<style>
body{
padding-top:50px;
}
</style>
这是怎麽回事？
全部代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<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>Bootstrap 101 Template</title>
<link href="file:///E|/网页（设计大赛）/dist/css/bootstrap.min.css" rel="stylesheet">
<style>
body{
padding-top:50px;
}
</style>
</head>
<body>
<nav class="navbar navbar-default navbar-fixed-top navbar-inverse" role="navigation">
<div class="container-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 class="navbar-brand" href="#">Brand</a>
</div>
<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
<ul class="nav navbar-nav">
<li class="active"><a href="#">Link</a></li>
<li><a href="#">Link</a></li>
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">Dropdown <span class="caret"></span></a>
<ul class="dropdown-menu" role="menu">
<li><a href="#">Action</a></li>
<li><a href="#">Another action</a></li>
<li><a href="#">Something else here</a></li>
<li class="divider"></li>
<li><a href="#">Separated link</a></li>
<li class="divider"></li>
<li><a href="#">One more separated link</a></li>
</ul>
</li>
</ul>
</div>
</div>
</nav>
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<script src="http://cdn.bootcss.com/jquery/1.11.1/jquery.min.js"></script>
<script src="file:///E|/网页（设计大赛）/dist/js/bootstrap.min.js"></script>
</body>
</html>
复制你的代码，在我这边测试没问题，可能是浏览器问题，或者是你引入css的问题