JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <iframe id="left_frame" src=""></iframe>
    <iframe id="right_frame" src=""></iframe>
</body>

CSS

#top_frame {
    width: 100%;
}
#left_frame {
    width: 50%;
}
#right_frame {
    width: 50%;
}
#bottom_frame {
    width: 100%;
}

#left_frame,
#right_frame { float: left; }

iframe {
    box-sizing: border-box;
}