JSFiddle - React, Tailwind, and code Playground

HTML

<div id="d1">
	<iframe id="f1" src="left.html"></iframe>
</div>
<div id="d2">
	<iframe id="f2" src="right.html"></iframe>
</div>

CSS

#d1, #d2
{
	position: absolute;
	border: 1px solid;
	z-index: 1;
}
#d1
{
	left: 0;
	top: 0;
	bottom: 0;
	width: 300px;
}
#d2
{
	right: 0;
	top: 0;
	bottom: 0;
	left: 300px;
}
#f1, #f2
{
	width: 99%;
	height: 99%;
}