<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
html,body{
width: 100%;
height: 100%;
font-size: 16px;
}
*{margin: 0;padding: 0;}
.box1{
width: 200px;height: 200px;
background: #eee;
margin-top: 10px;
/*定位居中*/
position: relative;
}
.box2{
width: 200px;height: 200px;
background: #eee;
margin-top: 10px;
/*margin居中*/
position: relative;
}
.box3{
width: 200px;height: 200px;
background: #eee;
margin-top: 10px;
/*inline居中*/
text-align: center;
}
/*定位+transform居中*/
.box1 div{border: 1px solid #000;position: absolute;left: 50%;top: 50%;transform: translate(-50%,-50%)}
/*margin居中*/
.box2 div{border: 1px solid #000;position: absolute;left: 0;top: 0;bottom: 0;right: 0;margin:auto;width: 100px;height: 50px}
/*inline居中*/
.box3 div{border: 1px solid #000;display: inline-block;vertical-align: middle;}
.box3:before{content: ''; display: inline-block; height: 100%; vertical-align: middle;}
</style>
</head>
<body>
<div class="box1">
<div>我想居中</div>
</div>
<div class="box2">
<div>我想居中</div>
</div>
<div class="box3">
<div>我想居中</div>
</div>
</body>
</html>
demo: https://controllerone.github.io/test/