- From: Jukka K. Korpela <jkorpela@cs.tut.fi>
- Date: Tue, 1 May 2007 00:00:20 +0300 (EEST)
- To: www-html@w3.org
On Mon, 30 Apr 2007, David Woolley wrote:
> Lachlan Hunt wrote:
>
>> Wrong! Error handling is one of the most important things to do
>> interoperably. Consider CSS, which does define precisely how to handle
>> errors gracefully. That is one case where the spec got it right and
>
> CSS doesn't define how to handle errors.
It does. For example, if you write
body { width: 600; }
then this is an error (missing unit after number), and browsers are
required to ignore the rule. And modern browsers do, except perhaps in
Quirks Mode. There are quite a many pages that use unitless values where
units are required, and error processing rules in CSS specifications
require that those pages be broken, instead of making the sensible
assumption (which e.g. IE makes in Quirks Mode) that the user meant
pixels.
It's definitely an error handling requirement. Whether it's a good
requirement is a different issue. Along the principles outlined for HTML
5, it would be obvious that the rules need to be changed to comply with
existing practice - except that this is CSS, not HTML, but I guess HTML 5
would soon be accompanied by CSS 3.2, which would be effectively CSS 2.1
with error handling requirements transmogrified and some cool new
features thrown in. :-)
> It defines how to successfully ignore future extensions.
That might be the motivation behind the rules, but the rules and their
implementations exist independently of that. (I won't even imagine what
possible extension to CSS would allow pure numbers as values for e.g. the
width property, given the fact that such values have widely been used to
denote pixels.)
> If people start authoring CSS that falls within
> the invalid CSS space, they risk finding their documents breaking in the
> future.
That's a risk with any use of extended features (i.e. features not in
specifications) and doesn't depend on error processing rules.
--
Jukka "Yucca" Korpela, http://www.cs.tut.fi/~jkorpela/
Received on Monday, 30 April 2007 21:00:29 UTC