background-attachment与background-position 的问题

background-attachment:fixed | scroll

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>练习 1</title>
    <style>
        body{
            margin: 0;
        }
        .backgroundCss{
            width: 400px;
            height: 600px;
            border: 1px solid indianred;
            background-color: blanchedalmond;
            background-image: url('img/background.png');
            background-repeat: no-repeat;
            background-position: right 100px;
            background-attachment: fixed;
        }
    </style>
</head>
<body>
    <div class="backgroundCss"></div>
</body>

效果：

理想效果为：

更改background-attachment:scroll即可解决。