templates/notfound.html

<title>404 Not Found</title>
<style>body {background-color:black;}div#a {font-family:Helvetica, system-ui, sans-serif;color:white!important;line-height:0.5;position: absolute;top: 50%;left: 50%;transform: translate(-50%, -50%);}</style>
<div id="a"><h1>404</h1><h2>Not found</h2></div>