JSFiddle - React, Tailwind, and code Playground

HTML

<div id="leftBanner">asdf</div>

<div id="mainContent"> asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf  asdf asdf asdf asdf asdf asdf asdf asd</div>

CSS

html, body {
      margin: 0;
      padding: 0;
      border: 0;
      height: 100%;
    }
#leftBanner {
	height: 100%;
	background-color: #CCC;
	width: 22%;
	min-width: 245px;
	max-width: 355px;
	float: left;
}
#mainContent {
	height: 2000px;
	background-color: red;
	opacity: .3;
	width: auto;
	float: left;
}