金山老师的笔记清除两测浮动
清除两侧浮动，有扩展父级盒子高度的作用
html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
.container{
border: solid 1px blue;
/* overflow:hidden; */
}
.class1 {
width: 200px;
height: 100px;
background: palegreen;
float: left;
}
.class2 {
width: 250px;
height: 130px;
background: gold;
float: left;
}
.class3 {
width: 300px;
height: 180px;
background: red;
float: left;
}
.clear{
clear: both;
}
</style>
</head>
<body>
<div class="container">
<div class="class1">我是块级元素1，没有设置浮动</div>
<div class="class2">我是块级元素2，没有设置浮动222222222222222222222222222222222222222</div>
<div class="class3">我是块级元素3，没有设置浮动</div>
<div class="clear"></div>
</div>
</body>
</html>