http://www.w3.org/TR/REC-html40

http://www.w3.org/TR/REC-html40

[1] Opera は 4 以降で XHTML名前空間として http://www.w3.org/TR/REC-html40 に対応しています。

Opera 7.54 と Opera 9 で確認
Web Specifications Supported in Opera http://www.opera.com/docs/specs/opera6/#xml-ns

[2] XLIFF 1.1 Specification ( 版) http://www.oasis-open.org/committees/xliff/documents/cs-xliff-core-1.1-20031031.htm#Struct_Extension_Attributes

[3] Namespace Scope, InetSDK, , https://web.archive.org/web/20001001011812/http://msdn.microsoft.com/xml/xmlguide/namespaces-scope.asp