Browsers are flexible pieces of software. They generally ignore elements whose names they aren't familiar with. In this case elements who aren't in the XHTML namespace are ignored by the brower and this RDF document may be viewed as HTML given some embedded XHTML elements.
This at least works on MS IE5.5 - "view source" demonstrates that this is actually an RDF document whose root element
is rdf:RDF
This is a description of the "L" language.
It is anticipated that many related-resource natures will be well known. A list of well-known natures may be found in the RDDL directory http://www.rddl.org/natures.