代码
提交代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.item{
width: 100px;
height: 100px;
text-align: center;
line-height: 100px;
border: 1px solid #ccc;
background: #f2f2f2;
}
.item:nth-child(3){
background: red;
}
</style>
</head>
<body>
<div class="demo">
<div class="item">1</div>
<div class="item">2</div>
<div class="item">3</div>
<div class="item">4</div>
</div>
</body>
</html>
运行结果