JSFiddle - React, Tailwind, and code Playground

HTML

<div id="pageWrapper">
            <header>
                Header
            </header>
            <div id="contentWrapper">
                    Content
            </div>
                <div id="navWrapper">
                    Nav
                </div>
        </div>

CSS

html, body{
    height: 100%;
}

body{
    background-color: #E3E3E3;
}

#pageWrapper{
    margin: 0 auto;
    position: relative;
    width: 600px;
    height: 100%;
}

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

#contentWrapper{
    width: 100%;
    height: 100%;
    background: blue;
}

#navWrapper{
    width: 100%;
    height: 100px;
    background: green;
}