清除浮动，margin重叠问题

清除浮动解决高度塌陷问题

	<div class="box1">
        <div class="box2"></div>
    </div>

	.box1{
		border: 10px red solid;
	}

	.box2{
		width: 100px;
		height: 100px;
		background-color: #bfa;
		float: left;
	}

通过添加.clearfix类清除浮动，解决margin重叠

	.clearfix::before,
	.clearfix::after {
		content:"";
		display:table;
		clear:both;
	}

	<div class="box1">
        <div class="box2 clearfix"></div>
    </div>