JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div id="header">
        <div id="navmenu">
        <ul>
            <li class="home"><a href="#">Home</a></li>
            <li><a href="#">Over ons</a></li>
                <li><a href="#">Projecten</a></li>
                <li><a href="#">Gallerij</a></li>
                <li><a href="#">Contact</a></li>
            </ul> 
                 
            
            
        </div>
    </div>

CSS

html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, dl, dt, dd, ol, ul, li, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed, figure, figcaption, footer, header, hgroup, menu, nav, output, ruby, section, summary, time, mark, audio, video {
 margin: 0;
 padding: 0;
 border: 0;
 font-size: 100%;
 font: inherit;
 vertical-align: baseline;
 }
body {
    margin: 0;
}
p {
    margin: 0;
}
#header {
    margin: 0;
    background: #a1a2a6;
    height: 200px;
    width: 100%;
    border-bottom: 5px solid #469;
    float: left;
}
#navmenu {
    margin-top: 100px;
    margin-left: 80px;
    height: 100px;
    width: 700px; 
 border: 1px solid #000;
}
#navmenu ul {
    margin-top: 42px;
    padding: 0;
    list-style: none;
}
#navmenu li {
    margin: 0;
    width: 100px;
    padding: 19px;
    font-family: Verdana;
    font-size: 15px;
    float: left;
    border: 1px solid #469;
    text-align: center;
}
#navmenu ul li a {
    text-decoration: none;
    color: #fff;
    display: block;
}
#navmenu li:hover {
    background: #469;
    transition: all .3s linear 0;
}
.home {
    background: #469;
}