You can specify the namespace and language of the <html> tag:
[HTMLOptions] ; XHNamespace default for XHTML 1.0 is "http://www.w3.org/1999/xhtml" ; Uncomment and give alternate if needed, do not leave blank ;XHNamespace=http://www.w3.org/1999/xhtml ; XHLanguage default is "en" ;XHLanguage=en ; XHLangAttr = xml:lang (default, set as needed; ; DocBook wants just lang) ;XHLangAttr=xml:lang
Although DITA2Go always produces valid code, it does not attempt to validate the content of your macros. We suggest you validate your document with the W3C’s free HTML validator:
http://jigsaw.w3.org/css-validator/
If your document is valid, you are offered a little graphic to include in it. See §22.14 Passing W3C validation tests.