左边DIV①的扩充内容DIV②(DIV②属于DIV①中的内容)如何显示在右边iframe的上方？

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<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
    <title> 页面名称 </title>
<style type="text/css">
#div1 {
    float: left;
    width: 200px;
    height: 500px;
    background-color: #99f;
    position: relative;
}
#div2 {
    position: absolute;
    left: 150px;
    top: 200px;
    z-index: 999;
    width: 200px;
    height: 100px;
    background-color: #9f0;
}
</style>
</head>
<body>
<div id="div1">
    <div id="div2"></div>
</div>
<iframe src="https://www.baidu.com" frameborder="0" width="600" height="500"></iframe>
</body>
</html>