JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main">
  <div class="header">header</div>
  <div class="content">
    <div class="block">content1</div>
    <div class="block">content2</div>
    <div class="block">content3</div>
  </div>
</div>

CSS

html,body{
  margin:0;
  background:#bbb;
}
.header{
  background:#999;
  height:50px;
}
.content{
  background:#999;
  margin:0 10%;
  border:1px solid transparent;
}
.block{
  height:50px;
  margin:5px;
  padding:5px;
  border:1px solid #000;
}