老师这样写正确吗

来源：2-18 编程练习

江伍德

2021-03-14 23:38:12

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {


            margin: 190px auto;
            font-family: Arial;
            font-size: 72px;
            font-weight: bold;
            position: fixed;
            right: 0;
            left: 0;
            bottom: 30px;
            width: 30px;
            height: 30px;
            margin:  auto;


            transform: rotate(90deg);

            animation: b 1s ease 0s infinite alternate;
        }
        @keyframes b{
            from{
                bottom: 30px;
            }
            to{
                bottom: 70px;
            }
        }
    </style>
</head>
<body>
    <div>&gt;</div>
</body>
</html>