第三种解决办法
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>01-04水平居中布局第四种</title>
<style>
.main{
width:500px;
height:100px;
background: #666;
display: flex;
justify-content: center;
}
.child {
width:100px;
height:100px;
background: red;
}
</style>
</head>
<body>
<div class="main">
<div class="child">
11111
1111111111
11111111111
11111111
</div>
</div>
</body>
</html>
