We have implemented the canonical url tag, within Aegir CMS, which allows you to define which page is authoritative. This complements our SEO tools, which already includes the hreflang tag element and both these features are explained below:
What is the canonical link element?
A canonical URL lets you tell search engines that certain similar URLs are actually the same. Sometimes you have products or content that can be found on multiple URLs, or even multiple websites, but by using canonical URLs (HTML link tags with the attribute rel=canonical), you can have these on your site without harming your rankings by telling search engines which page is the preferred version of that page.
What is the hreflang element?
hreflang tags are a technical solution for sites that have similar content in multiple languages. The owner of a multilingual site wants search engines to send people to the content in their own language. Say a user is French and the page that ranks is English, but there’s also a French version. You would want Google to show the French page in the search results for that French user. This is the kind of problem hreflang was designed to solve.