<div class="container" >
<ul type='circle'>
<li>1</li>
<li>2</li>
<li>3</li>
</ul>
</div>
<style>
*{
padding: 0;
margin: 0;
}
.container{
border: 1px solid black;
}
.container::after{
content:'';
display: block;
clear: both;
}
body{
height:2000px;
}
ul li{
float: left;
width: 50px;
}
</style>
三件套:
① 给浮动元素的父级元素加伪类,content为:‘’
②display:block;
③clear:both;