Searching for Yocto documentation turns out to be difficult. A search for "Poky environment-setup" points to the ancient o-hand documentation but not to the Yocto website. Searching "Yocto ADT Manual" gives a google page that says that the robots.txt prevents google from indexing the page. Looking at the robots.txt I see a "Disallow: /" which might explain it.
I think Michael has fixed this already after I discussed it with him directly - Michael, can you confirm?
https://www.yoctoproject.org/robots.txt was was copied over from the development server during the last security update set on June 5th. Fixed at 2013-06-20 16:00.