Is <html lang = "de-DE"> equal to <meta http-equiv = "language" content = "DE">?
According to Google Multilingual Recommendations :
Google uses only the visible content of your page to determine its language. We do not use any code level information such as lang.
SEO . URL-:
Google , URL . , URL- .ca fr : http://example.ca/fr/vélo-de-montagne.html http://fr.example.ca/vélo-de-montagne.html.
, (. Rahul Tripathi answer), html 5. .
, hreflang , , .
google docs
HTML5 meta http-equiv="Language" . <html lang="de-DE">.
HTTP Content-Language , , . Content-Language http-equiv . language html, .
Content-Language , :
Content-Language . , .