JSFiddle - React, Tailwind, and code Playground

HTML

<header></header>

    <section></section>
    <aside></aside>
    <footer></footer>

CSS

body{
	width: 1024px;
height: 612px;
margin: 0 auto; 
	}

header {
position: relative;
top: 0;
width: 100%;
height: 100px;
box-sizing: border-box;
background-color: blue; }

section {
position: relative;
margin: 0;
padding: 0;
width: 70%;
height: 600px;
box-sizing: border-box;
background-color: red;
display: inline-block;
float: left;}

aside {
position: relative;
margin: 0;
padding: 0;
left: 0;
width: 30%;
height: 600px;
box-sizing: border-box;
background-color: green;
display: inline-block; }