404.html

<html>
  <head>
    <title>404 Error</title>
    <style>
      body {
        font-family: arial;
        text-align: center;
        color: black;
      }
    </style>
  </head>
  <body>
    <h1>404 Error</h1>
    <h2>Looks like this page doesn't exist!</h2>
    <h2>Requested URL: <span id="full">Fetching...</span></h2>
    <script>
      document.getElementById("full").innerText = window.location.href;
    </script>
  </body>
</html>