JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container" class="clearfix">
    <div id="right-sidebar">Right</div>
    <div id="left-sidebar">Left</div>
</div>

CSS

#container {
    width: 200px;
    border: 2px solid blue;
    padding: 2px;
    margin: 0;
}

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

#left-sidebar, #right-sidebar {
    width: 150px;
    padding: 2px;
}

#left-sidebar {
    border: 2px solid red;
    float: left;
}

#right-sidebar {
    border: 2px solid green;
    float: right;
}