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CSS2 cascade order

From: Charles McCathieNevile <charlesn@sunrise.srl.rmit.edu.au>
Date: Thu, 18 Dec 1997 17:37:32 +1100
Message-ID: <3498C4A8.96378B23@srl.rmit.edu.au>
To: jongund@staff.uiuc.edu, w3c-wai-ig@w3.org
I have been discussing this matter about a bit. The problem is that
sub-classes are difficult to over-ride, and that in any case the cascade
order gives priority to the author.

The _recommendation_ is that it be possible to ignore authors' style
sheets.

This seems to me a roundabout way to solve a straightforward problem.
The two parts two a sensible solution are:
1. Reverse the cascade order, so a reader's style sheet over-rides an
authors. (As I read CSS2, even though readers do not write a style
sheet, a compliant browser presents their preferences AS IF they were a
style sheet) This simply requires a change in the way browsers interpret
the cascade, and would cause no legacy problems as there is no new
element being introduced.
The benefit is that, where particular parts of styles are over-ridden,
it avoids throwing the author's baby out with the bathwater - their
style participates in the cascade, and only elements chosen by the user
such as FONT, or COLOR, or whatever are over-ridden.

2.The difficulty introduced by sub-classes has been extensively
commented on in the wai interest group list. The best solution is to
allow the specificity of a user declaration to be declared, rather than
determined by the rules.
for example: H1 !CLASS font:symbol colour:aqua would override any class
of H1, but not a declaration for a H1 specified by ID, where as H1
!CLASS !ID or H1 !ALL would be treated as being specific to every single
instance of an H1.
This approach does require some new elements to be added, but again
provides a flxible approach which allows as much of the author's style
to be included as appropriate, rather than simply having to reject all
or nothing.

Charles McCathieNevile
Sunrise Research Laboratory
RMIT University
Received on Thursday, 18 December 1997 01:38:41 GMT

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