404.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>404 - Page Not Found</title>
  <style>
    body {
      font-family: Arial, sans-serif;
      text-align: center;
      background-color: #f5f5f5;
      margin-top: 50px;
    }
    h1 {
      font-size: 80px;
      color: red;
    }
    p {
      font-size: 20px;
    }
    button {
      padding: 10px 20px;
      font-size: 16px;
      background-color: royalblue;
      color: white;
      border: none;
      border-radius: 5px;
      cursor: pointer;
    }
    button:hover {
      background-color: darkblue;
    }
  </style>
</head>
<body>
  <h1>404</h1>
  <p>Oops! Page Not Found.</p>
  <button onclick="window.location.href='index.html'">Go Back Home</button>
</body>
</html>