<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
* {
margin: 0;
padding: 0;
}
.box {
300px;
margin: 0 auto;
}
ul {
list-style: none;
}
.box .item {
float: left;
148px;
border: 1px solid blue;
background: blue;
color: #f0f0f0;
line-height: 40px;
text-align: center;
}
.item:hover {
background: lightblue;
}
/* > 子代选择器*/
.item>ul{
display: none;
background: #f0f0f0;
color: black;
}
.item:hover ul{
display: block;
}
.item li:hover{
color: blue;
}
</style>
</head>
<body>
<ul class="box">
<li class="item">视频教程
<ul>
<li>全部视频教程</li>
<li>Java教程</li>
<li>Python教程</li>
<li>HTML教程</li>
</ul>
</li>
<li class="item">认证考试
<ul>
<li>全部认证</li>
<li>Java认证</li>
<li>Python认证</li>
<li>HTML认证</li>
</ul>
</li>
</ul>
</body>
</html>效果
