Extension headers and caching

Hi,

If I perform a request to a server and then perform a subsequent request  
with an extension header set, should I get a cached copy or a fresh one  
for the subsequent request? Would it be different if the server had  
replied with a Vary header for the extension header?

It has been suggested that I should define how this case works in  
XMLHttpRequest, but I rather just defer to the HTTP for this.

Kind regards,


-- 
Anne van Kesteren
<http://annevankesteren.nl/>
<http://www.opera.com/>