JSFiddle - React, Tailwind, and code Playground

HTML

<div id="nav"><ul><li>one</li><li>two</li><li>three</li></ul>
</div>
<div id="top">more</div>
<div id="middle">fun</div>

CSS

#nav { position: absolute;border: red 1px solid; background: gray; z-index: 100; padding: 0px; margin: 0 0 0 20px; }

#nav li {
    line-height: 2em;
    padding: 25px;
}

#top {width: 100%;height: 150px;background: yellow; }

#middle { width: 100%; height: 300px; background: green;}