I didn't see anything in there about app banners.
(In case it's changed the headline currently says: "Google downranks sites that do mobile redirects / app banners".)
EDIT: seems it was a different, but very similar article - https://developers.google.com/webmasters/smartphone-sites/co...
I didn't see anything in there about app banners.
(In case it's changed the headline currently says: "Google downranks sites that do mobile redirects / app banners".)