Problem with Unicorn

Hi QA,

I tried the Unicorn validation service and encountered a problem:

There appears an error message

shall be written as
See HTML Compatibility Guideline 7: The lang and xml:lang Attributes

whenever you use a lang attribute in XHTML without also having an 
xml:lang attribute.

My reading of the referenced HTML Compatibility Guideline C.7 from the 
XHTML 1 spec is that, for compatibility with HTML user agents, you 
should not use only an xml:lang attribute, which an HTML user agent will 
not understand, but add a lang attribute. The HTML Compatibility 
Guidelines do not address compatibility with generic XML user agents, 
which could be expected to understand xml:lang, but not XHTML's lang 
attribute. Requiring an xml:lang attribute does not enhance 
compatibility with HTML user agents.

So the error message should only appear, if there is only an xml:lang 
attribute without an accompanying lang attribute in XHTML.

Greetings
-- 
Johannes Koch
Fraunhofer Institute for Applied Information Technology FIT
Web Compliance Center
Schloss Birlinghoven, D-53757 Sankt Augustin, Germany
Phone: +49-2241-142628    Fax: +49-2241-142065