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Action-504 new rewrites for 2.9.1

From: Jim Allan <jimallan@tsbvi.edu>
Date: Thu, 17 Feb 2011 16:19:34 -0600
Message-ID: <AANLkTikndd9hu96fQxV5967MemUyvFdHi+EeTusn4Ze4@mail.gmail.com>
To: WAI-ua <w3c-wai-ua@w3.org>
2.9.1 (former 4.9.1) Improve Foreground Legibility: The user can have
all background images shown. hidden or replaced. (Level A)

Intent:
It can be difficult for people with vision problems or distraction
problem to read text or identify images when the background is complex
or doesn't contrast well with the foreground. Allowing users to
disable the display of background images or replace the image with a
solid color helps ensure that foreground content remains easy to read.
This can also help remove purely decorative distractions, which is
important for some users.

Users should have the option to have non-transparent backgrounds of a
solid color of their choice drawn behind text, rather than turning off
background images. This ensures that foreground text does not
disappear when the image is removed and the default background color
does not provide sufficient contrast with the foreground text color.
As an aid to selecting an appropriate background color, the user agent
could programmatically determine the foreground text color and suggest
a range of background colors.

Because background images occasionally convey important information,
when their display is turned off the user agent should give users
access to any alternative content associated with them.

This checkpoint applies to background that are unambiguously defined
as being written on the base background, such as the HTML background
property. It does not apply to cases where complex computation is
required to determine whether or not some content will appear behind
or overlap other content, as with the multi-layered renderings(refer,
for example, to the z-index property in Cascading Style Sheets, level
2 ([CSS2], section 9.9.1)

Examples:
James has a reading disability where he needs text to be clear from
distractions that are not related to the text. He configures his user
agent not to load background images and navigates to a web page. James
then gets only the text from the web page without any images
interfering with what he is reading.

Related Resources:
1. In CSS, background images may be turned on/off with the background
and background-image properties ([CSS2], section 14.2.1).

2. The z-index property in Cascading Style Sheets, level 2 ([CSS2],
section 9.9.1)

3. Because background images occasionally convey important
information, when their display is turned off the user agent should
give users access to any alternative content associated with them. (At
the time of this writing, HTML does not support alternative content
for background images, but this may be supported in other technologies
or future versions.)

4. See Success Criteria 1.4.1 "Configure Text" for more information
related to background colors.


-- 
Jim Allan, Accessibility Coordinator & Webmaster

Texas School for the Blind and Visually Impaired

1100 W. 45th St., Austin, Texas 78756

voice 512.206.9315    fax: 512.206.9264  http://www.tsbvi.edu/

"We shape our tools and thereafter our tools shape us." McLuhan, 1964
Received on Thursday, 17 February 2011 22:20:10 GMT

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