JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="main">Main content goes here. This part I want to be fluid width, while the sidebar should be fixed. Try resizing the window/frame.</div>
    <aside>Sidebar content goes here</aside>
</div>

CSS

#container {
    max-width: 600px; /* bigger in production */
    margin: 0 auto;
    background: #BAE9E9;
}
#main, aside {
    display: table-cell;
    padding: 10px;
}
aside {
    width: 100px;
    background: #8AB9B9;
}