The REL attribute is used to give the relationship(s) described by the hypertext link - consequently REL cannot be used unless an HREF is present. The value for REL is a comma-separated list of relationship values. For example
<A HREF="http://foo.edu/fe.html" REL="Usindex">sdfsddf</a>Values for the relationships and their semantics are registered by the HTML registration authority. The default relationship is none. For more information see the CERN HTML Documentation -- the relationships and their uses are described in The CERN documentation refered to in the bibliography.