JSFiddle - React, Tailwind, and code Playground

HTML

<div id="header">12345</div>

CSS

body {
	position: relative;
	background-color: yellow;
	border: 10px solid red;
	width: 750px;
	height: 750px;
}

#header {
	position: absolute;
	background-color: blue;
	width: 100px;
	height: 100px;
	border: 3px solid black;
	left: 325px; top: 325px;
}