Let's consider the following url in the context of a multi-language website, whose default language is english:

http:www.website.com/en/ -> website loads in English
http:www.website.com/fr/ -> website loads in French
http:www.website.com/ -> website loads in English (default)

Two questions:


How do you handle:
http:www.website.com/erfn/, where ernf is a non-existing language. So far, I trigger the default language. But what bothers me is that the url looks valid, especially at the eyes of a bot. Should I 404? Redirect to the default url? What type of redirect in this case?

These two urls:
have the same content. It's a problem, indexing wise, if I'm not mistaking. So if the language set in the url is the default language, do you redirect to the url without any language specification, thus "erasing" the "en/" part?