Re: xkcd: LTR

From: Philippe Verdy <>
Date: Tue, 27 Nov 2012 15:50:12 +0100

Also you make a confusion in the sense that HTML5 must be able to "parse"

This is true, but this does not mean that they will be able to render it
fully. HTML5 is not fully upward compatible with past versions (and the
case of the identification of encodings is an example where it is
different, and many requirements of HTML4 are no longer requirements in
HTML5 due to some relaxed rules after the faield effort to standardize
HTML4 more like XHTML and according to the initial CSS specifications).

So HTML5 renderers will just render HTML4 in a "best effort", but lots of
requirements that are applicable to real *HTML5* documents (identified by
their prolog) do NOT apply to non-HTML5 documents as they are not directly
in scope of its standard (hte HTML4 specifications themselves are not
dismissed) : the best effort implies flexibility, even if interoperability
is not warrantied across HTML5 implementations that will all parse HTML4
documents but may still produce different results (inclusing with the
support of HTML4 quirk mode if they want).

2012/11/27 Masatoshi Kimura <>

> (2012/11/27 20:27), Philippe Verdy wrote:
> > HTML5 does not reference the "Content-Type: text/html" header as enough
> > to qualify as meaning "HTML5".
> HTML5 User-agents must parse any byte sequences as HTML5 document if the
> Content-Type is text/html.
> > HTML5 **requires** its own prolog (i.e. its basic document declaration
> > **within** the document itself, for the HTML syntax, or its FULL
> > document declaration for the XML/XHTML syntax).
> HTML5 requires **authors** to write the prolog, not user-agents. Lacking
> prolog just turn the user-agents to quirks mode.
> Note that quirks mode doesn't mean "do whatever you consider it quirks."
> Parsing quirks mode document is also completely spec'ed.
> > So Firefox is wrong and attempts to use HTML5 to render all HTML
> dialects.
> No, not at all. Rather, it is required by the spec to use HTML5 parser
> to parse all byte sequences sent with "Content-Type: text/html".
> Could you please stop spreading an unfounded rumor such as "Firefox is
> wrong because it ignores the lacking of HTML5 prolog"?
> --
Received on Tue Nov 27 2012 - 08:51:32 CST

This archive was generated by hypermail 2.2.0 : Tue Nov 27 2012 - 08:51:32 CST