lib/middleware/notfound.html

<!DOCTYPE html>
<html>
<head>
<title>{{ title }}</title>
<style>
    html, body {
        margin: 0;
        padding: 0;
        font-family: sans-serif;
        background: #eeeeee;
    }

    li {
        margin: 0.8em;
    }

    #header {
        background-color: #cccccc;
    }

    #header h1 {
        font-weight: normal;
        font-size: 28px;
        margin: 0;
    }

    h3 {
        font-weight: normal;
    }

    #body {
        background-color: #ffffff;
    }

    #header, #body {
        padding: 30px;
        border-bottom: 1px solid #aaaaaa;
    }
</style>
</head>
<body>
<div id="header"><h1>{{ title }}</h1></div>
<div id="body">
{{ body }}
</div>
</body>
</html>