404.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8"/>
    <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
    <title>404</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            font-family: system-ui, -apple-system, "Segoe UI", Roboto, Oxygen,
            Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif;
        }

        body {
            background-color: #212529;
            color: #dee2e6;
        }

        #wrapper {
            display: flex;
            background-color: #212529 !important;
            border: none;
            width: 80%;
            height: 90vh;
            margin: 5vh auto;
            justify-content: center;
            align-items: center;
            vertical-align: middle;
            border-radius: 25px;
        }

        #content {
            text-align: center;
        }

        h1 {
            font-size: 30vh;
            line-height: 30vh;
        }

        h2 {
            margin: 2vh 0;
        }

        h2,
        p {
            color: #a1a8ae;
        }

        a {
            color: rgb(110, 168, 254);
        }
    </style>
</head>
<body>
<div id="wrapper">
    <div id="content">
        <h1>404</h1>
        <h2>Oops! Page not found</h2>
        <p>Sorry, the page you're looking for doesn't exist. Please, go to <a href="/">main page</a>.</p>
    </div>
</div>
</body>
</html>