JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrapper">
    <div id="header">Header and top links in here</div>
    <div id="container">
     <div id="content">Main content area</div>
    </div>
</div>

CSS

html, body, #container { height: 100%; }
body { z-index:1; position:relative; }
body > #wrapper { height:100%; margin:0 auto; width:400px; }
body > #wrapper > #header { z-index:3; position:relative; height:100px; background:#ccc; }
body > #wrapper > #container { z-index:2; position:relative; height:auto; min-height:100%; background:#eee; margin-top:-100px; padding-top:100px; box-sizing:border-box; }