xml:lang="" vs HTTP
Assertion holds if you see green below.
This test is only valid if the user agent recognises the HTTP and html xml:lang declarations, and :lang works.
|Ignore this test. (:lang not supported)|
Assertion: If the HTTP header contains a language declaration but the html element uses an empty xml:lang attribute, the UA will not recognize the language declared in the HTTP header.
Red means the HTTP had precedence.