css对于IE7、FF、OP清除浮动的最优方法

2020-11-27 来源：华佗健康网

在CSS森林群里讨论一个margin的问题中无意间发现overflow也可以用来清除浮动，嘿嘿，这个方法不单使用简单，而且FF、OP、IE7都支持，从此可以告别那又长兼容性又差的FF清浮动的方法了。

方法真的很简单，只要为需要清浮动的标签加上overflow这个属性。
css代码

ul {
	list-style: none;
	height: auto;
	margin: 0;
	p adding: 0;
	background-color: #436973;
}
li {
	float: left;
	width: 80px;
	height: 80px;
	background-color: #83B1DF;
}
.demo {
	clear: both;
	border: 1px solid #FF00FF;
	margin-bottom: 5px;
}
.overflow {
	overflow: auto;
	zoom: 1;
	background-color: #43FF73;
}
ul {
	list-style: none;
	height: auto;
	margin: 0;
	padding: 0;
	background-color: #436973;
}
li {
	float: left;
	width: 80px;
	height: 80px;
	background-color: #83B1DF;
}
.demo {
	clear: both;
	border: 1px solid #FF00FF;
	margin-bottom: 5px;
}
.overflow {
	overflow: auto;
	zoom: 1;
	background-color: #43FF73;
}

HTML代码

<div class="demo">
	<ul class="overflow">
	<li>1</li>
	<li>2</li>
	<li>3</li>
	<li>4</li>
	<li>5</li>
	<li>6</li>
	<li>7</li>
	<li>8</li>
	<li>9</li>
	</ul>
</div>
<div class="demo">
	<ul>
	<li>1</li>
	<li>2</li>
	<li>3</li>
	<li>4</li>
	<li>5</li>
	<li>6</li>
	<li>7</li>
	<li>8</li>
	<li>9</li>
	</ul>
</div>

其中zoom是为了IE6准备的。

<?xml version="1.0" encoding="utf-8"?> 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh-cn"> 
<head> 
<meta http-equiv="pragma" content="no-cache" /> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<meta http-equiv="Content-Language" content="utf-8" /> 
<meta name="robots" content="all" /> 
<meta name="author" content="Ghost" /> 
<meta name="Copyright" content="CSSForest" /> 
<meta name="Description" content="CSS?" /> 
<meta name="Keywords" content="CSS,web标准,web,Blog,,XHTML,CSSForest,CSS森林" /> 
<title>Overflow hack Demo|www.CSSForest.org</title> 
<link rel="Shortcut Icon" href="/favicon.ico" type="image/x-icon" /> 
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript"></script> 
<script type="text/javascript">_uacct = "UA-780254-5";urchinTracker();</script> 
<style type="text/css"> 
/*<![CDATA[*/ 
.copyright{position:absolute;bottom:60px;left:10px;width:300px;height:200px;line-height:1.2em;} 
.copyright a:link{color:#666666;text-decoration:none;} 
.copyright a:hover{color:#CC9900;text-decoration:underline;} 

ul{list-style:none;height:auto;margin:0;padding:0;background-color:#436973;} 
li{float:left;width:80px;height:80px;background-color:#83B1DF;} 
.demo{clear:both;border:1px solid #FF00FF;margin-bottom:5px;} 
.overflow{overflow:auto;zoom:1;background-color:#43FF73;} 
/*]]>*/ 
</style> 
</head> 

<body> 
<p></p> 
<div> 
 <ul> 
 <li>1</li> 
 <li>2</li> 
 <li>3</li> 
 <li>4</li> 
 <li>5</li> 
 <li>6</li> 
 <li>7</li> 
 <li>8</li> 
 <li>9</li> 
 </ul> 
</div> 
<div> 
 <ul> 
 <li>1</li> 
 <li>2</li> 
 <li>3</li> 
 <li>4</li> 
 <li>5</li> 
 <li>6</li> 
 <li>7</li> 
 <li>8</li> 
 <li>9</li> 
 </ul> 
</div> 

<div> 
 <div> 
 <div><img src="http://img68.imageshack.us/img68/8708/mylogo9we.gif" alt="LOGO" /></div> 
 <div> 
 <p class="fn n"><strong>Ghost</strong> <strong>Zhang</strong></p> 
 <p><strong>Email:</strong><a href="mailto:lovej1bz@gmail.com">lovej1bz@gmail.com</a></p> 
 <p><strong>QQ:</strong><a href="tencent://message/?uin=22168741&Site=webrebuild.org&Menu=yes">22168741</a></p> 
 <p><strong>ORG:</strong><a href="http://www.webrebuild.org">WebReBuild.ORG</a> <a href="http://www.cssforest.org/">www.CSSForest.ORG</a></p> 
 <strong>Blog:</strong><a href="http://forest.blogbus.com" rel="me">http://forest.blogbus.com</a> </div> 
 </div> 
</div> 
</body> 
</html>

注：忘了一个很重要的内容，并不是所有的overflow属性都可起来一样的效果，比如visible属性就只能对IE起作用。例子可以看这里：

<?xml version="1.0" encoding="utf-8"?> 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh-cn"> 
<head> 
<meta http-equiv="pragma" content="no-cache" /> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<meta http-equiv="Content-Language" content="utf-8" /> 
<meta name="robots" content="all" /> 
<meta name="author" content="Ghost" /> 
<meta name="Copyright" content="CSSForest" /> 
<meta name="Description" content="CSS?" /> 
<meta name="Keywords" content="CSS,web标准,web,Blog,,XHTML,CSSForest,CSS森林" /> 
<title>Overflow hack Demo|www.CSSForest.org</title> 
<link rel="Shortcut Icon" href="/favicon.ico" type="image/x-icon" /> 
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript"></script> 
<script type="text/javascript">_uacct = "UA-780254-5";urchinTracker();</script> 
<style type="text/css"> 
/*<![CDATA[*/ 
.copyright{position:absolute;bottom:60px;left:10px;width:300px;height:200px;line-height:1.2em;} 
.copyright a:link{color:#666666;text-decoration:none;} 
.copyright a:hover{color:#CC9900;text-decoration:underline;} 

ul{list-style:none;height:auto;margin:0;padding:0;background-color:#436973;} 
li{float:left;height:80px;margin-right:2px;padding:0 10px;background-color:#83B1DF;line-height:80px;} 
.demo{clear:both;border:1px solid #FF00FF;margin-bottom:5px;} 
.overflow{overflow:auto;zoom:1;background-color:#43FF73;} 
.overflow1{overflow:hidden;zoom:1;background-color:#43FF73;} 
.overflow2{overflow:visible;zoom:1;background-color:#43FF73;} 
/*]]>*/ 
</style> 
</head> 

<body> 
<p>overflow的visible属性只对IE起作用，auto/hidden可对FF、OP起作用。</p> 
<div> 
 <ul> 
 <li>overflow:auto;</li> 
 <li>overflow:auto;</li> 
 <li>overflow:auto;</li> 
 <li>overflow:auto;</li> 
 <li>overflow:auto;</li> 
 <li>overflow:auto;</li> 
 </ul> 
</div> 
<div> 
 <ul> 
 <li>overflow:hidden;</li> 
 <li>overflow:hidden;</li> 
 <li>overflow:hidden;</li> 
 <li>overflow:hidden;</li> 
 <li>overflow:hidden;</li> 
 <li>overflow:hidden;</li> 
 </ul> 
</div> 
<div> 
 <ul> 
 <li>overflow:visible;</li> 
 <li>overflow:visible;</li> 
 <li>overflow:visible;</li> 
 <li>overflow:visible;</li> 
 <li>overflow:visible;</li> 
 <li>overflow:visible;</li> 
 </ul> 
</div> 
<div> 
 <ul> 
 <li>no overflow</li> 
 <li>no overflow</li> 
 <li>no overflow</li> 
 <li>no overflow</li> 
 <li>no overflow</li> 
 <li>no overflow</li> 
 </ul> 
</div> 


<div> 
 <div> 
 <div><img src="http://img68.imageshack.us/img68/8708/mylogo9we.gif" alt="LOGO" /></div> 
 <div> 
 <p class="fn n"><strong>Ghost</strong> <strong>Zhang</strong></p> 
 <p><strong>Email:</strong><a href="mailto:lovej1bz@gmail.com">lovej1bz@gmail.com</a></p> 
 <p><strong>QQ:</strong><a href="tencent://message/?uin=22168741&Site=webrebuild.org&Menu=yes">22168741</a></p> 
 <p><strong>ORG:</strong><a href="http://www.webrebuild.org">WebReBuild.ORG</a> <a href="http://www.cssforest.org/">www.CSSForest.ORG</a></p> 
 <strong>Blog:</strong><a href="http://forest.blogbus.com" rel="me">http://forest.blogbus.com</a> </div> 
 </div> 
</div> 
</body> 
</html>

这样的话就有一个问题啦，如果要有高度，而且内容超出高度的时候，定义auto或hidden都可能会有一些不想要的效果出现。这里提供一个解决方案：对于IE6及以下版本的IE，可以直接定义高度；对于IE7、FF、OP，可定义min-height。

css代码：

overflow 
{ 
height:auto; 
_height:200px; 
min-height:200px; 
verflow:auto; 
zoom:1; 
_overflow:visible; 
}

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css对于IE7、FF、OP清除浮动的最优方法