JSFiddle - React, Tailwind, and code Playground

HTML

<html>
    <body>
        <div class="holder">
            <div class="centered">
                CENTERED
            </div>
            <div class="sidebar">
                RIGHT SIDEBAR
            </div>
        </div>
    </body>
</html>

CSS

div.centered {
    margin-left: auto;
    margin-right: auto;
    border: dashed;
    width: 100px;
    height: 100px;
}

div.sidebar {
    border: dotted;
    float: left;
}