iframe_url = "http://www.amazon.com/reviews/iframe?[...snip...]"
iframe = Nokogiri::HTML(open(iframe_url))

OpenURI::HTTPError: 403 Forbidden

%iframe{:src => "http://www.amazon.com/reviews/iframe?[...snip...]"}/

iframe_url = "http://www.amazon.com/reviews/iframe?[...snip...]"
html = "<iframe src = #{iframe_url}></iframe>"
iframe = Nokogiri::HTML(html)