mechanize：Mechanize::Page#content_type

>> require 'mechanize'
=> true
>> agent = Mechanize.new
=> #<Mechanize:0xb74a22e0 ...
>> page = agent.get('http://google.com/')
=> #<Mechanize::Page
 {url #<URI::HTTP:0xb7491ea4 URL:http://www.google.co.jp/>}
 {meta}
  ...

>> page.content_type
=> "text/html; charset=Shift_JIS"