How can I embed my rails app into another website via iframe?

It works nicely with RoR 3, but not with RoR 4:

<iframe src="http://myrailsapp.com/" width="100%" height="50" id="rails_iframe">error!</iframe>

I tried to use verify_authenticity_token and protect_from_forgery options in my controller... seems it's something else (but I'm not sure).

upd. Example: http://jsfiddle.net/zP329/

ruby-on-rails ruby-on-rails-3 iframe ruby-on-rails-4
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