<!DOCTYPE html>
<html>
<body>
    <div style="margin-bottom: 10px; width: 60px; height: 40px;">
        <div style="margin-bottom: 10px; width: 60px; height: 40px;">
            <div style="margin-bottom: 20px; width: 60px; height: 40px;"></div>
        </div>
    </div>
</body>
</html>