application.html.erb

<!-- Hold it in application.html.erb or ur own default layout. for this example put in navigator. -->
<% if @win_ie_with_chromeframe %>
<script>
navigator.chromeframe = true;
</script>
<% end -%>

application_controller.rb

# Detect chrome frame in application_controller.rb
before_filter :chromeframe_detect

protected
def chromeframe_detect
  ua = request.user_agent
  @win_ie_with_chromeframe = ua =~ /Windows NT/ and ua =~ /MSIE (\d+)/ and $1.to_i < 9 and ua =~ /chromeframe/
end