<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
.a1{
width: 300px
;
height: 300px
;
background-color: pink
;
position: relative
;
}
.a2{
width: 100px
;
height: 100px
;
background-color: rosybrown
;
position: absolute
;
margin: auto
;
top: 0
;
bottom: 0
;
right: 0
;
left: 0
;
}
</style>
</head>
<body>
<div class=
"a1">
<div class=
"a2"></div>
</div>
</body>
</html>
