Use ‘rel’ and ‘hreflang’ for translations. Links to alternate language versions should use rel=“alternate” and e.g. hreflang=“es” for the Spanish version. The alternate rel value signifies an alternate version of the current page, and hreflang signifies the language of the page at the href (in contrast to the lang attribute which signifies the language of the contents of the element.).

8 steps to serving better (X)HTML