abstract：<!DOCTYPE html><html> <head> <meta charset="UTF-8"> <title></title>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style>
*{
margin:0;
padding:0;
}
ul,li,ol{
list-style:none;
}
.nav-list{
width:600px;
margin:0 auto;
}
.nav-list > li{
display:inline-block;
margin:5px -3px;
padding:3px 15px;
position:relative;
}
.nav-list > li:before{
content:'';
position:absolute;
bottom:0px;
width:0;
left:50%;
border-bottom:2px solid red;
transition:0.2s all linear;
}
.nav-list > li:hover::before{
left:0;
width:100%;
}
.nav-list > li:hover + li::before{
left:0;
}
</style>
</head>
<body>
<ul class="nav-list">
<li>导航导航1</li>
<li>导航导航2</li>
<li>导航导航3</li>
<li>导航导航4</li>
</ul>
</body>
</html>
Correcting teacher：天蓬老师Correction time：2019-04-10 10:24:14
Teacher's summary：你的学生用户名, 怎么没有显示呢? 看一下你的用户设置, 设置一个名字