> What *could* a browser do with unrecognized elements, other
> than ignore them? Barf? That's not very robust. Flag
> them as an error? That might even be useful. Invoke a new
I would have been quite happy if the various browsers I test with
had had an option to flag my unintended introduction on invalid HTML.
Would have been much better than silence combined with not getting the
expected result.
> experimental feature? That's been *demonstrated* to be
> useful.
>
> Ignoring unrecognized elements and attributes is clearly a
> good implementation strategy, and it is appropriate to
> assume that browsers are implemented this way when
> designing HTML extensions. However, a specification
> defining a *document format* has no business describing
> what implementations should do with documents that *do not
> conform* to that format.
I tend to agree.