JSFiddle - React, Tailwind, and code Playground

HTML

<header></header>

<div>Test</div>

CSS

header {
    background: none repeat scroll 0 0 #283744;
    border-bottom: 4px solid #4F5B66;
    height: 97px;
    margin-top: 0;
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 999;
}

div {
    margin-top: 97px;
    width: 100%;
    height: 200px;
    position: fixed;
    background: #eee;
}