TheMadScientist - 1:56 pm on Oct 22, 2012 (gmt 0)
just to be clear, "code-level" language information is distinct from "link-level" language information, which is the proprietary "link rel alternate hreflang" attribute google began supporting last year.
Good to note the separation, but even though support of it maybe be limited to Google* it's not a proprietary attribute: (Standard in HTML 4.01 & HTML 5 according to w3schools.org HTML hreflang Attribute [w3schools.com])
12.3 Document relationships: the LINK element
%attrs; -- %coreattrs, %i18n, %events --
charset %Charset; #IMPLIED -- char encoding of linked resource --
href %URI; #IMPLIED -- URI for linked resource --
hreflang %LanguageCode; #IMPLIED -- language code --
type %ContentType; #IMPLIED -- advisory content type --
rel %LinkTypes; #IMPLIED -- forward link types --
rev %LinkTypes; #IMPLIED -- reverse link types --
media %MediaDesc; #IMPLIED -- for rendering on these media --
Links in HTML Documents [w3.org]
* I should note: I don't know if it's recognized by Google only, because I don't deal with multilingual sites unless I have to, but I remembered seeing it in the HTML docs when I read through the link section and thought I should point out it's not some new 'Google only thing' they decided to invent on us.