JSFiddle - React, Tailwind, and code Playground

HTML

<body>
<div id="container">
	<div id="hdr-lay">
	Header
	</div>

	<div id="left-column">
	Grid Layout left
	</div>

	<div id="right-column">
	Grid Layout right
	</div>
</div>
</body>

CSS

#hdr-lay {
	_background-color: red;
}

#container {
    background-color: gray;
	height:100%;
	width:100%;
}


#left-column {
	float: left;
    background-color: red;
	border: 1px;
	width: 70%;
}

#right-column {
    float: left;
	width: 30%;
    background-color: blue;
	display: block;
}