W3C home > Mailing lists > Public > www-style@w3.org > December 1997

Re: Backwards compatibility of new selectors (was: Color models and CSS2 in general)

From: Liam Quinn <liam@htmlhelp.com>
Date: Tue, 02 Dec 1997 16:44:56 -0500
Message-Id: <>
To: www-style@w3.org
Hash: SHA1

At 03:25 PM 02/12/97 -0500, Douglas Rand wrote:
>Liam Quinn wrote:
>> The CSS1 Recommendation states that "A ruleset that starts with a 
>> string that is not valid CSS1 is skipped." [1]  Since the ~ and /
>> characters are not permitted in a CSS1 selector-string unless escaped 
by a
>> backslash [1], a selector such as /MATH ~ P/ will cause the entire 
>> to be ignored in CSS1 browsers.
>Anybody actually try this with IE4 or NS4 to make sure that they
>*do* ignore them?

Of course they don't.  The section on forward-compatible parsing was 
towards the end of the CSS1 Recommendation, so most implementors would 
have stopped reading.  (Netscape 4 actually comes close to compliance on 
this issue; the browser ignores rules with ~ and /, but it doesn't ignore 
the ruleset.)

>And why make this particularly difficult... it
>is certainly possible to do this without adding funky characters.

If you don't add funky characters you don't have backwards compatibility 
with CSS1-compliant browsers.

>You're relying on proper error behavior - always a bad thing to do
>(no matter what the spec said).

So the forward-compatibility requirements of CSS1 should be ignored by 
future CSS standards just because some implementors have problems reading 
to the end of the spec?

>I found the spec to be pretty difficult
>to decipher at times - I probably wasn't alone.

No, you weren't, but the section on forward-compatible parsing was quite 
clear, IMO.
>> If by "first generation" you mean claiming to support CSS1, then I 
>> there's a much more serious problem:  Users with first generation 
>> are going to be pretty upset when they find out their browsers don't
>> really support CSS1.
>Not an argument for breaking bc.  As above - the spec is not easy
>to follow.  It is not suprising that nobody has it right.

The forward-compatibility section is easy to follow.  It's still not 
surprising that nobody got it right, but that's just my pessimism towards 
the browser vendors and their ability to implement something they didn't 

>> >In fact the syntax for CSS2 had better
>> >be forward and backward compatible.
>> I believe it is.  The forward-compatibility requirements of CSS1 are 
>> well thought out.  Too bad browser vendors haven't implemented them.
>This is a very poor way of looking at the world.  There are realities
>to deal with which don't go away just because they're ignored.

I don't think that CSS2 should be held back because of backwards 
compatibility concerns in buggy implementations.  If that were the case, 
we'd have to deprecate em and ex units (IE3 bugs), backslash escaping in 
selectors (Netscape 4 bug), percentage font sizes (IE3), and a slew of 
other features.  The current CSS implementations are at such an infantile 
stage that I don't think that those writing the CSS2 draft should concern 
themselves with browser bugs.  <ANALOGY CLASS=dumb>You don't reform the 
education system just because 2-year-olds can't pass high 

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Liam Quinn
Web Design Group            Enhanced Designs, Web Site Development
http://www.htmlhelp.com/    http://enhanced-designs.com/
Received on Tuesday, 2 December 1997 16:43:53 UTC

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