Use of rel="alternate" hreflang="x"

[IM_Learner]

Google states that use of rel="alternate" hreflang="x" is recommended when:

• You translate only the template of your page, such as the navigation and footer, and keep the main content in a single language. This is common on pages that feature user-generated content, like a forum post.

• Your pages have broadly similar content within a single language, but the content has small regional variations. For example, you might have English-language content targeted at readers in the US, GB, and Ireland.

• Your site content is fully translated. For example, you have both German and English versions of each page.

Does this mean that if I write new content in different language for a website hosted on my sub-domain, I should not use this tag?

Regards,

Shailendra Sial

[john4math]

Looking at http://googlewebmastercentral.blogspot.com/2011/12/new-markup-for-multilingual-content.html and http://support.google.com/webmasters/bin/answer.py?hl=en&answer=189077, you would only want to implement rel=alternate tags when the content is duplicate content.  So if you write new content in a different language on a subdomain that doesn't appear on your main domain in a different language, don't specify a rel=alternate.  If it's a translation of content on your main domain, go ahead and add it.

The difference in the implementation when you have pages with completely different languages vs. small regional differences is if the pages are in completely different languages, you won't want to implement canonical tags pointing to one of the variations.

Re-reading through those articles, it's not 100% clear to me what adding this does when you don't implement the canonical tags.  Google says "This markup tells Google's algorithm to consider all of these pages as alternate versions of each other."