With regards to the idea of ignored tags in HTML+ the Internet draft,
by David Raggett (dsr@hplb.hpl.com) dated July 1993, states on page 4
'Notes to Implementors' that unknown tags should be simply ignored.
This ignoring of `unknown' tags should fit nicely into your
requirements.
It was also indicated, in an earlier mail message to www-talk, that
unknown attributes of known tags will also be ignored.
Fred Williams
fwilliam@ccs.carleton.ca