Multi-language website - unique URLs required for different languages (to prevent caching)?
I have developed an AppEngine/Python/Django application that currently works in Spanish, and I am in the process of internationalizing with multi-language support. It is basically a dating website, in which people can browse other profiles and send messages. Viewing a profile in different languages will result in some of the text (menus etc) being displayed in whichever language is selected, but user-generated content (ie. user profile or message) will be displayed in the original language in which it was written.
My question is: is it necessary (or a good idea) to use unique URLs for the same page being displayed in different languages or is it OK to overload the same URL for a given page being displayed in different languages. In particular, I am worried that if I use the same URL for multiple languages, then some pages might be cached (either by Google, or by some other proxy that I might not be aware of), which could result in an incorrect language being displayed to a user.
Does anyone know if this is a legitimate concern, or if I am worrying about something that will not happen?
In principle, you can use the Content-Language and Vary response headers and the Accept-Language request header to control how caches behave and to prevent them serving up the wrong language to users.
In practice, however, Accept-Language is frequently set incorrectly in browsers, which is why most sites don't rely on it, or at least provide a secondary mechanism. Caches may be similarly unreliable about respecting the Vary header, but I'm not sure. Having language-specific URLs is certainly a practical way to do it, and avoids any potential issues with caching.