<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#qqq {
cursor: pointer;
border: 1px solid; width: 300px; height: 300px;
}
#qqq::after {
border: 1px solid green; width: 50px; height: 50px;
content: "oops!";
}
#qqq:hover::after {
background-color: red;
}
</style>
</head>
<body>
<div id="qqq"></div>
</body>
</html>
<hr/>
;