@tikpage/reactjs-popup/docs/src/pages/404.js

React Popup Component - Modals,Tooltips and Menus — All in one

import React from 'react';
import Layout from '../components/Layout';

const NotFoundPage = () => (
  <Layout>
    <div>
      <h1>NOT FOUND</h1>
      <br />
      <p> 404 - Oh no's! We couldn't find that page :( </p>
    </div>
  </Layout>
);

export default NotFoundPage;