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Re: Checkpoint 3.4 relative vs absolute

From: Charles McCathieNevile <charles@w3.org>
Date: Tue, 18 Jun 2002 05:42:31 -0400 (EDT)
To: Jason White <jasonw@ariel.ucs.unimelb.edu.au>
cc: "Virant, Michael W" <Virant.Michael.W@edumail.vic.gov.au>, "'w3c-wai-gl@w3.org'" <w3c-wai-gl@w3.org>
Message-ID: <Pine.LNX.4.30.0206180531470.20796-100000@tux.w3.org>

On Tue, 18 Jun 2002, Jason White wrote:

  Virant, Michael W writes:
   > Please confirm that absolute values in a CSS file still pass checkpoint 3.4 as
   > long as I've validated that the rendered content is usable.

  That seems to be what WCAG 1.0 is saying, as I read the checkpoint.

Aah. One of those rare occasions when Jason and I disagree. As I read the
checkpoint "Use relative rather than absolute units in markup language
attribute values and style sheet property values" using absolute size values
fails it.

Michael quoted:

http://www.w3.org/WAI/wcag-curric/sam32-0.htm written by Chuck Letourneau

  "For example, in CSS, use 'em' or percentage lengths rather than 'pt' or
  'cm', which are absolute units. If absolute units are used, validate that
  the rendered content is usable by checking the results on various
  browsers or systems."

As I read this it is going beyond the checkpoint. My interpretation is that
if you use absolute values you fail to meet the checkpoint. Even if you fail
to meet the checkpoint, you should try to minimise the actual problems this
causes. (That works as a general principle - not just for this checkpoint).

Often it is difficult to get size and positioning right in complex layouts.
In many of these cases simplifying the layout is helpful for users, as well
as for the designer trying to make their layout work accessibly. Complex
layouts of links, especially, often arise because too much is being squeezed
into one page. Although this helps to compensate for the fact that browsers
never seem to quite manage to get bookmarks perfect (they should be more like
authoring web links and less like some magic different thing, but most
browsers are built on the assumption that the Web is more like TV than an
interactive place for knowledge sharing), it makes pages hard to use for
anyone. (I would cite any number of government and large corporate pages I
use as a regular Australian as evidence - finding a link among 60 or 120 is
difficult, and harder when they have been styled to blend into each other...)

Like Jason, I am not representing any group opinion here, just my personal


Charles McCN
Received on Tuesday, 18 June 2002 05:42:37 UTC

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