解决包裹浮动元素问题

	
		
		
		
	
	
		

			
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*{
	margin: 0px;
	padding: 0px;	
}
.wrapper{
	border: black 1px solid;
}
.wrapper::after{
	
	content: "";
	clear: both;
	display: block;
}
.content{
	float: left;
	background-color: black;
	width: 100px;
	height: 100px;
	color: beige;
}

利用伪类：

.wrapper::after{
    
    content: "";
    clear: both;
    display: block;
}