Hi. The '@@html:...@@' markers allow to embed raw HTML. Unfortunately, they are not rendered in any special way in the Emacs editing mode, AFAIU.
It would be interesting, I think, to be able to colorize them, and/or mask them somehow visually, to not clutter the plain org editing. I haven't found instructions for reporting feature requests for org, so feel free to direct me to a more appropriate venue. Hope ths helps. Best regards, -- Olivier BERGER http://www-public.telecom-sudparis.eu/~berger_o/ - OpenPGP-Id: 2048R/5819D7E8 Ingenieur Recherche - Dept INF Institut Mines-Telecom, Telecom SudParis, Evry (France)