- From: Tantek Çelik <tantek@cs.stanford.edu>
- Date: Thu, 01 Apr 2004 16:28:11 -0800
- To: Boris Zbarsky <bzbarsky@MIT.EDU>, Ian Hickson <ian@hixie.ch>, <www-style@w3.org>
On 4/1/04 12:29 PM, "Boris Zbarsky" <bzbarsky@MIT.EDU> wrote: > restrictions required by CSS2 non-compliant AFAICT, that clause is the source of the confusion. That clause doesn't make any sense. The only restrictions required are to ignore values that you do not understand. CSS is made of levels. Each level adds to the next (for the most part). Conforming to one level (e.g. CSS1) does not make you "non-conformant" to the next level, it just means you only support that one level, and perhaps you only partially support the next level. E.g. the background-position property in CSS1 allowed a certain set of values. In CSS2.1, additional sets of values were allowed. Thus a CSS1 implementation of background-position understands a certain set of values. A CSS2.1 implementation understands more values. A CSS1 implementation is *expected* to ignore those new values. There is nothing wrong with that. Profiles similarly restrict which sets of values an implementation can be expected to understand. Adding new values to properties does not "break" old implementations. Those old implementations simply remain implementations of the old values. Same thing with which properties can apply to various pseudo-elements. It makes sense that latter levels allow/expect more properties to work on various pseudo-elements. This is how CSS forward/backward compatibility works. Tantek
Received on Thursday, 1 April 2004 19:28:35 UTC