JSFiddle - React, Tailwind, and code Playground

HTML

<body>
	
		<header>
		</header>
		<div id="maincontent">
		</div>
		<footer>
		</footer>
	
</body>

CSS

html, body {height:100%;padding:0; margin:0;}

    header{
        background-color:red; 
        height:1.8em;
    }
    #maincontent{
        background-color:black; 
        width: 100%;
        height: 100%;

    }
    footer{
        background-color:yellow;
        height:50px;
    }