第一种方法
定位1
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
*{
margin: 0;
padding: 0;
}
#container{
height: 600px;
overflow: hidden;
}
#div{
height: 200px;
width: 200px;
background: blue;
position: absolute;
top: calc(50% - 100px);
left: calc(50% - 100px);
}
</style>
</head>
<body>
<div id="container">
<div id="div"></div>
</div>
</body>
</html>
第二种方法
定位（拉扯的感觉）
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
*{
margin: 0;
padding: 0;
}
#div{
height: 200px;
width: 200px;
background: blue;
position: absolute;
top: 0;
bottom: 0;
right: 0;
left: 0;
margin: auto;
}
</style>
</head>
<body>
<div id="div"></div>
</body>
</html>
第三种方法
弹性盒子
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
*{
margin: 0;
padding: 0;
}
#container{
display: flex;
height: 600px;
background: red;
align-items: center;
justify-content: center;
}
#div{
height: 200px;
width: 200px;
background: blue;
}
</style>
</head>
<body>
<div id="container">
<div id="div"></div>
</div>
</body>
</html>