@Otyugh yes I tested it a bit some time ago. The user:pass method is not implemented and deprecated by RFC-3986 in section 3.2.1:
https://www.rfc-editor.org/rfc/rfc3986#section-3.2.1
Looking at snac2 source it looks they use Basic HTTP Auth, so Dillo should prompt you the user/pass once per process.
@grunfink would it be posible to use cookies to store a login token?, otherwise the password will end up stored in plain text.