Success Criterion 3.1.1 (Language of Page) states that the primary language of the page must be specified to qualify for single-A conformance.
This example should successfully test the usage of lang and xml:lang attributes on the HTML element.
Note: This example document is a HTML serialisation of HTML5, which explicitly allows both "lang" and "xml:lang" - but only the former takes effect, as in HTML 4.01. (If this were XHTML, the latter would prevail, as per the XML definition.) In HTML 4.01 and earlier, the presence of "xml:lang" would make the document invalid, although not necessarily failing any Success Criteria.
(The "*" represents either "Lang" or "XmlLang" depending on which attribute applies.)