<!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>
.box {
600px;
height: 40px;
line-height: 50px;
background: #ffa4b2;
text-align: center;
color: white;
font-size: 20px;
}
span {
0;
height: 0;
/*background: white;*/
border: 5px solid transparent;
border-top: 5px solid #ffffff;
display: inline-block;
position: relative;
top: 2.5px;
left: 8px;
}
.item ul {
list-style: none;
padding: 10px;
}
.box:hover span {
border: 5px solid transparent;
border-bottom: 5px solid #ffffff;
top: -2.5px;
}
.box .item {
float: left;
148px;
color: #f0f0f0;
line-height: 40px;
text-align: center;
}
.item:hover {
background: lightblue;
}
li{
}
/* > 子代选择器*/
.item > ul {
display: none;
background: lightblue;
color: white;
}
.item:hover ul {
display: block;
}
.item li:hover {
color: blue;
}
</style>
</head>
<body>
<div class="box">
<div class="item">导航1<span></span>
<ul>
<li>Java教程</li>
<li>Python教程</li>
<li>HTML教程</li>
</ul>
</div>
<div class="item">导航2<span></span>
<ul>
<li>Java教程</li>
<li>Python教程</li>
<li>HTML教程</li>
</ul>
</div>
<div class="item">导航3<span></span>
<ul>
<li>Java教程</li>
<li>Python教程</li>
<li>HTML教程</li>
</ul>
</div>
<div class="item">导航4<span></span>
<ul>
<li>Java教程</li>
<li>Python教程</li>
<li>HTML教程</li>
</ul>
</div>
</div>
</body>
</html>
