* David Woolley wrote:
>The only sites I know of that do do server side negotiation of anything
>but User Agent (using procedural, rather than declarative code, in that
>case) are Google, some versions of Microsft's Windows Update page and
>some images on the W3C site.  None of these can effectively use 
>q factors as the common browsers do not allow the users to configure
>them, relying on positional fallback instead.

They do for Accept-Language and there are quite a number of sites that
use Accept-Language for content negotiation.