cache,page

http://www.javaworld.com.tw/jute/post/view?bid=59&id=191117&sty=3&age=0&tpg=1&ppg=1
http://api.rubyonrails.org/classes/ActionController/Caching/Pages.html#M000282

# In Rails 2.1 you can use :if option
caches_page :index, :if => Proc.new { |c| !c.request.format.json? } <=不是json才會cache