JSFiddle - React, Tailwind, and code Playground

HTML

<body>

<div id="wrap">
<div id="blue"></div>    
<div id="red"></div>
    <div class="clr"></div>
</div>

</body>

CSS

#wrap {
	border: 4px solid black;
	width: 100%;
}
.clr{clear:both;}
#blue {
	width: 300px;
	height: 300px;
	background-color: blue;
	float: left;
}

#red {
	width: 300px;
	height: 300px;
	background-color: red;
	float: left;

}