JSFiddle - React, Tailwind, and code Playground

HTML

<body>
	<div class="wrapper">
		<header>
			<div class="left"></div>
			<div class="middle"></div>
			<div class="right"></div>
		</header>
	</div>
</body>

CSS

* {
	margin: 0;
	padding: 0;
	-webkit-box-sizing: border-box;
	-moz-box-sizing: border-box;
	-ms-box-sizing: border-box;
	box-sizing: border-box;
	
}

.wrapper {
	width: 1000px;
	margin: 0 auto;
}

header:after {
	content: ".";
	display: block;
	visibility: hidden;
	height: 0;
	clear: both;
}

.left {
	float: left;
	width: 300px;
	height: 195px;
	background: #888;
	border: 1px solid #000;
}

.middle {
	float: left;
	width: 350px;
	height: 195px;
	background: #888;
	border: 1px solid #000;
}


.right {
	float: right;
	width: 350px;
	height: 195px;
	background: #888;
	border: 1px solid #000;
}