Resource Description Framework In Attributes (RDFa) is a means of embedding RDF (ResourceDescriptionFramework) information as attributes in XHTML. This enables a web page to contain semantic information which can be extracted by suitable software.
http://en.wikipedia.org/wiki/RDFa
RDFaCE provides an editor for RDFa: http://aksw.org/Projects/RDFaCE
I have put in this link as the WikiPedia page for RDFaCE ( http://en.wikipedia.org/wiki/RDFaCE ) is proposed for deletion and it seems to be useful information. -- JohnFletcher