JSFiddle - React, Tailwind, and code Playground

HTML

<div class="sitebar"></div>
<div class="content"></div>

CSS

.sitebar{
  float: left;
  width: 30%;
  height: 300px;
  background-color: #cc0000;
}
.content{
  float: left;
  width: 70%;
  height: 300px;
  background-color: #00cc00;
}