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批改状态：合格
老师批语：定位的参照非常的重要
一、浮动布局
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.left{float: left; width: 200px; height: 200px; background: paleturquoise;}
.right{float: right; width: 200px; height: 200px; background: palegoldenrod;}
</style>
</head>
<body>
<div class="left">float:left 左浮动</div>
<div class="right">float:right 右浮动</div>
</body>
</html>
浮动对父级元素的影响：造成父级元素高度折叠为0
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.box{ background: #DDDDDD;}
.left{float: left; width: 200px; height: 200px; background: paleturquoise;}
.right{float: right; width: 200px; height: 200px; background: palegoldenrod;}
</style>
</head>
<body>
<div class="box">
<div class="left">float:left 左浮动</div>
<div class="right">float:right 右浮动</div>
</div>
</body>
</html>点击 "运行实例" 按钮查看在线实例
解决方法：
!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.box{ height:200px; background: #DDDDDD; margin-top: 20px;}
.left{float: left; width: 200px; height: 200px; background: paleturquoise;}
.right{float: right; width: 200px; height: 200px; background: palegoldenrod;}
.box2{overflow: hidden; background: palevioletred; margin-top: 20px;}
.clearfix{clear: both;}
.box3{background: greenyellow; margin-top: 20px;}
.box4{float: left; width: 100%; background: darkcyan; margin-top: 20px;}
.box5{background: #009F95; margin-top: 20px;}
.clearfixs:after{content:"."; display:block; height:0; clear:left; visibility:hidden;}
</style>
</head>
<body>
<div class="box">
1：为父级设置高度
<div class="left">float:left 左浮动</div>
<div class="right">float:right 右浮动</div>
</div>
<div class="box2">
2：为父级设置 overflow: hidden; 样式
<div class="left">float:left 左浮动</div>
<div class="right">float:right 右浮动</div>
</div>
<div class="box3">
3：为父级中插入样式为 clear:both 的空标签
<div class="left">float:left 左浮动</div>
<div class="right">float:right 右浮动</div>
<div class="clearfix"></div>
</div>
<div style="overflow: hidden;">
<div class="box4">
4：为父级 也设置浮动元素
<div class="left">float:left 左浮动</div>
<div class="right">float:right 右浮动</div>
</div>
</div>
<div class="box5 clearfixs">
5：使用CSS的:after伪元素
<div class="left">float:left 左浮动</div>
<div class="right">float:right 右浮动</div>
</div>
</body>
</html>点击 "运行实例" 按钮查看在线实例
二、三列布局
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.box{ height:200px; background: #DDDDDD;overflow: hidden;}
.left{float: left; width: 200px; height: 200px; background: paleturquoise;}
.right{float: right; width: 200px; height: 200px; background: palegoldenrod;}
.box2{position: relative; height: 200px; background: #DDDDDD; margin-top: 20px; text-align: center;}
.aLeft{position: absolute; left: 0; top: 0; bottom: 0; width: 200px; background: paleturquoise;}
.aRight{position: absolute; right: 0; top: 0; bottom: 0; width: 200px; background: palegoldenrod;}
.box3{display:flex; height: 200px; background: #DDDDDD; margin-top: 20px; text-align: center;}
.fLeft{width: 200px; height: 200px; background: paleturquoise;}
.fRight{width: 200px; height: 200px; background: palegoldenrod;}
.fMain{flex: 1;}
</style>
</head>
<body>
<div class="box">
1，通过浮动布局
<div class="left">float:left 左浮动</div>
<div class="right">float:right 右浮动</div>
</div>
<div class="box2">
2，通过position: relative 定位布局
<div class="aLeft">position: absolute;绝对定位left:0</div>
<div class="aRight">position: absolute;绝对定位right:0</div>
</div>
<div class="box3">
<div class="fLeft">左边固定</div>
<div class="fMain">3，通过display:flex布局</div>
<div class="fRight">右边固定</div>
</div>
</body>
</html>点击 "运行实例" 按钮查看在线实例
总结：float 和 position 都会使元素脱离文档流，就是脱离了自身原本的位置，按最近的同样拥有float或position的父级元素重新定位自身的位置。
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