private void installContentLanguage(String language) {
        if (contentLanguageSeen) {
            return;
        }
        contentLanguageSeen = true;

        String lang = "";
        boolean langSpecified = false;
        if (language != null) {
            try {
                if (!"".equals(language)) {
                    Language.THE_INSTANCE.checkValid(language);
                }
                lang = language;
                langSpecified = true;
            } catch (DatatypeException e) {
            }
        }
        if (!langSpecified) {
            return;
        }

        int i = 0;
        for (Node node : stack) {
            if (i == 0) {
                // nop
            } else if (i == 1) {
                node.lang = lang;
                node.langSpeficied = true; // probably unnecessary...
            } else {
                if (node.langSpeficied) {
                    return;
                } else {
                    node.lang = lang;
                }
            }
            i++;
        }
    }
-1 at start
0 in html
>=1 in head
-2 situation over
src/nu/validator/xml/BaseUriTracker.java