404.html

<html lang="en">
  <head>
    <title>404: Page not found</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1.0, user-scalable=no"/>
    <!-- CSS -->
    <link href="assets/css/main.css" type="text/css" rel="stylesheet">
    <link href="https://fonts.googleapis.com/css2?family=Source+Code+Pro&display=swap" rel="stylesheet">

    <!-- Custom CSS -->
    <style>
      .cursor { animation: 1s blink step-end infinite; font-weight: bolder; }
      @keyframes blink {
        from, to { opacity: 0; }
        50% { opacity: 1; }
      }
    </style>
  </head>
  <body>
    <section class="fullscreen">
      <div class="background" style="background-image: url('https://media.tenor.com/images/d5d51c0c23a6fe6b5e445939044e6b65/tenor.gif');"></div>
      <div class="center-object center-text">
        <h1 class="bold">
          <span style="color: #e74c3c;">404</span>
            <br>
          Page not found<span class="cursor">_</span>
        </h1>
        <a href="/" class="btn" style="border: 3px solid #e74c3c; height:auto">Back to home</a>
      </div>
    </section>
  </body>
</html>