Da rfc2396 Sezione 4.1
When a URI reference is used to perform a retrieval action on the identified resource, the optional fragment identifier, separated from the URI by a crosshatch ("#") character, consists of additional reference information to be interpreted by the user agent after the retrieval action has been successfully completed.
E dalle specifiche html4.01

http://www.w3.org/TR/html4/struct/li...ent_identifier
Destination anchors in HTML documents may be specified either by the A element (naming it with the name attribute), or by any other element (naming with the id attribute).
Quindi qualsiasi tag può essere indicato in un'ancora. Tuttavia il fragment identifier e' nomepagina#valore_attr_name se la destinazione e' un'A, nomepagina#valore_attr_id altrimenti.

PS:Quella del name per l'A non la sapevo.