JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="header"> 
            this is the header div.
    </div>
    <div id="content">
        This is the content div.
    </div>
</div>

CSS

#container {
  width: 100%;
  height: 100%;
  position: absolute;
  background: red;
}

#header {
    background: yellow;
    width: 100%;
    height: 100px;    
}

#content {
    background: green;
    width: 80%;
    height: 200px;
    margin-left:auto;
    margin-right:auto;
}