JSFiddle - React, Tailwind, and code Playground

HTML

<header><div id="mydiv"></div></header>
    <div id="content"><p>hello</p></div>

CSS

header { position: relative; background-color:#CCCCCC; width:960px; height:430px;}
#mydiv {position: absolute; top:0px; left: 0px; width:960px; height:320px; margin:80px 0px 0px 0px; background-color:#CC0000; }