Since you can store the locale of the user in the session, it may be tempting to use the same URL to display a resource in different languages based on the user's locale. For example,
could show content in English for one user and French for another user. Unfortunately, this violates a fundamental rule of the Web: that a particular URL returns the same resource regardless of the user. To further muddy the problem, which version of the content would be indexed by search engines?