default-app/html/error.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>Error {code}</title>
  </head>
  <body>
    <h1>Error {code}</h1>
    <h2>{long}</h2>
    <p>{text}</p>
    <code>Error instance: {id}</code>
    {internal_error&
    <h3>Debug info</h3>
    <p>The error leading up to this was:</p>
    <pre>
      {internal_error}
    </pre>
    }
  </body>
</html>