static/50x.html
<!doctype html>
<html lang="en">
<meta charset="utf-8">
<title>Server Error</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
html, body {
padding: 0;
margin: 0;
height: 100%;
}
p {
position: absolute;
width: 100%;
top: 5%;
color: #555555;
text-align: center;
font: 24px sans-serif;
}
</style>
<p>
Sorry, but the server has encountered an unexpected error.
</p>