Character encoding mismatch

I have just localised a site into Chinese (GB2312)

The thing is that when I go to the site on the net my browser doesn't pick 
up that it is GB2312 and instead keeps it as (iso-8859-1). I have to 
manually change the encoding for the page to view properly. This doesn't 
happen when I view other sites with the same encoding.

When I ran a check at W3C I got the following message:

Warning: Character Encoding mismatch! The character encoding specified in 
the HTTP header (ォiso-8859-1サ) is different from the one specified in the 
META element (ォgb2312サ).

I have just create a subfolder in the web e.g 
<http://www.domain.com/chinese>www.domain.com/<http://www.domain.com/chinese 
 >chinese Is this happening because the browser is reading the encoding 
rom <http://www.domain.com>www.domain.<http://www.domain.com>com and not 
/chinese? Does /chinese have to be converted into a subweb or something?

I would be grateful if someone could shed some light for me here.

Thanks in advance.
Chris