JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="right">Right</div>
    <div class="left">Left</div>
</div>

CSS

.container {
  width:70%;
}

.container, .left, .right {
  float:none;
  display:-moz-box;
  display:-webkit-box;
  -webkit-box-orient: vertical;
  -moz-box-orient: vertical;
}

.left {
  width:70%;
  background-color:#00a;
  color:#ddd;
  -moz-box-ordinal-group: 1;
  -webkit-box-ordinal-group: 1;
}

.right {
  width:30%;
  background-color:#0a0;
  -moz-box-ordinal-group: 2;
  -webkit-box-ordinal-group: 2;
}