JSFiddle - React, Tailwind, and code Playground

HTML

<script src=" https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.3/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/modernizr/2.8.3/modernizr.min.js"></script>
<div id="browserupgrade">
        <p>You are using an outdated browser. Please <a href="http://browsehappy.com/">upgrade your browser</a> to improve your experience.</p>
    </div>
 <div id="supports">
this browser supports flexbox
 </div>

CSS

#browserupgrade{
            display:none;
            text-align:center;
            background:#F1070B;
            color:#FFFFFF;
            font-family:Segoe, "Segoe UI", "DejaVu Sans", "Trebuchet MS", Verdana, sans-serif;
            font-size:15px;
            padding:10px;}

        #browserupgrade a{
            color:#FFFFFF;
            background:#000000;
            text-decoration:none;
            padding:5px 15px;
            border-radius:25px;}
        #supports{
         display:none;
        }

JavaScript

$(document).ready(function () {
    if (!Modernizr.flexbox) { $("#browserupgrade").show(); }
    else{$("#supports").show();}
});