JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="left"></div>
    <div id="right"></div>
    <div id="iframe"></div>
</div>

CSS

#container { position:relative; margin:auto; background-color:#000; width:300px; height:600px; overflow:auto; }
#left { float:left; width:75px; height:200px; background-color:red; }
#right { float:right; width:75px; height:200px; background-color:blue; }
#iframe { position:absolute; width:75px; height:200px; left:75px; background-color:green; }