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css样式表中第一个样式效果出不来，另外发现，只要div的设置哪个在第一个，第一个的样式就出不来。比如现在header排在第一个，header就没样式，nav排第一个nav就没样式。
<!DOCTYPE html>
<html>
<head>
<title>MY FIRST PAGE</title>
<link rel="stylesheet" type="text/css" href="sample.css">
</head>
<body>
<div id="header">
<h1>City Gallery</h1>
</div>
<div id="nav">
London<br />
Paris<br />
Tokyo<br />
</div>
<div id="section">
<h1>London</h1>
<p>
London is the capital city of England. It is the most populous city in the United Kingdom,
with a metropolitan area of over 13 million inhabitants.
</p>
<p>
Standing on the River Thames, London has been a major settlement for two millennia,
its history going back to its founding by the Romans, who named it Londinium.
</p>
</div>
<div id="footer">
Copyright W3School.com.cn
</div>
</body>
</html>css的代码如下。
<style>
#header{
background-color:black;
color:white;
text-align:center;
padding:5px;
}
#nav{
line-height:30px;
background-color:#eeeeee;
height:300px;
width:100px;
float:left;
padding:5px;
}
#section{
width:350px;
float:left;
padding:10px;
}
#footer{
background-color:black;
color:white;
clear:both;
text-align:center;
padding:5px;
}
</style>请大家帮帮我，感觉问题解决不了好难受，流泪。。。
html5
