index_1.html

<!DOCTYPE html>
<html>
    <head>
        <title>My First subwindow</title>
        <style>
            #inner-window{
                height: 200px;
                width: 300px;
                border: 2px solid black;
                box-align: "middle"; 
            }
        </style>
    </head>
    <body>
        <iframe id="inner-window" src="https://www.google.com/webhp?igu=1">

        </iframe>
    </body>
</html>