margin-top: 50%;
50%:对应的是父元素的宽度的50%
第一种方法
定位
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
#div {
width: 100px;
height: 100px;
background-color: red;
position: absolute;
left: 0;
top: 0;
right: 0;
bottom: 0;
margin: auto;
}
</style>
</head>
<body>
<div id="div"></div>
</body>
</html>
第二种方法
弹性盒子模型
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
#div1{
height: 500px;
background-color: yellow;
display: flex;
justify-content: center;
align-items: center;
}
#div {
width: 100px;
height: 100px;
background-color: red;
}
</style>
</head>
<body>
<div id="div1">
<div id="div"></div>
</div>
</body>
</html>
第三种方法
定位后偏移
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
#div2{
width: 100px;
height: 100px;
background-color: red;
position: absolute;
top: 50%;
left: 50%;
margin-left: -50px;
margin-top: -50px;
}
</style>
</head>
<body>
<div id="div2">
</div>
</body>
</html>