一：消除子元素浮动造成父元素高度折叠的影响
实例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.box1 {
width: 300px;
border: 5px dashed red;
}
.box2 {
width: inherit;
height: 300px;
background-color: blue;
}
.box2 {
float: left;
}
.box1 {
overflow: hidden;
}
</style>
</head>
<body>
<div class="box1">
<div class="box2">子元素块</div>
</div>
</body>
</html>运行实例 »
点击 "运行实例" 按钮查看在线实例
二、绝对定位实现, 浮动定位实现三列布局
1.绝对定位实现
实例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<style>
.main {
height: 800px;
position: relative;
}
.left {
height: 800px;
width: 200px;
background-color: yellow;
position: absolute;
left: 0;
top: 0;
}
.content {
height: 800px;
width: 800px;
background-color: lightcoral;
position: absolute;
left: 200px;
top: 0;
}
.right {
height: 800px;
width: 200px;
background-color: lightgreen;
position: absolute;
left: 1000px;
top: 0;
}
</style>
<title>绝对定位演示</title>
</head>
<body>
<div class="main">
<div class="left"></div>
<div class="content"></div>
<div class="right"></div>
</div>
</body>
</html>运行实例 »
点击 "运行实例" 按钮查看在线实例
2.浮动定位实现
实例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>浮动定位实现</title>
</head>
<style>
.content {
height: 700px;
width: 600px;
background-color: lightpink;
float: left;
}
.left {
height: 700px;
width: 300px;
background-color: blue;
float: left;
}
.right {
height: 700px;
width: 300px;
background-color: green;
float: left;
}
</style>
<body>
<div class="left"></div>
<div class="content"></div>
<div class="right"></div>
</body>
</html>运行实例 »
点击 "运行实例" 按钮查看在线实例
总结
消除子元素浮动造成父元素高度折叠的影响有好几种：
将父级元素的浮动与子元素的浮动同样
将父元素的高度与浮动的子元素同样
添加一个清除浮动div clear属性标签消除
父级元素css代码中添加个overflow: hidden;消除
以上方法都可以用，但第4种各种浏览器兼容，适用更规范
绝对定位与浮动定位都可以实现三列布局，视写代码的时候想用哪个就哪个看需求用