JSFiddle - React, Tailwind, and code Playground

HTML

<div id="sidebar">blah</div>
<div id="content">sfd</div>

CSS

* { margin:0; padding:0; }

#sidebar { float:left; width:280px; height:500px; background:blue; }
#content { margin:0 0 0 280px; height:500px; background:red; }