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Re: Why specify a DOCTYPE? Why validate?


From: Jon Gunderson
Date: May 30, 2002 6:45AM


One of the most important reasons to validate is that it makes sure that
people with disabilities can use a wider range of web technologies to
access web information. People with disabilities tend to use less main
stream technologies to access web documents and use more specialized
technologies that don't repair HTML like popular browsers like Netscape
Navigator and Microsoft Internet Explorer. I have heard that about two
thirds of the code in these browsers is used to repair invalid HTML
(software bloat). So just because a web page works one of these browsers
doesn't mean it will work on less popular browsers. The best way to do
that is to validate documents to the HTML standards. This not only helps
people with disabilities, but helps all users by giving them more options
to access web content.

The web works best when people use the standards to maximize interoperability.


At 09:18 AM 5/30/2002 -0400, you wrote:
>First off, let me disclaim the question by saying that I maintain a site
>of several hundred pages which all validate as XHTML 1.1 and are all
>Section 508 compliant. (They would be Bobby AAA compliant too, if Bobby
>were a little less buggy, but that's a different topic.) I write about
>accessibility from time to time, and I practice what I preach.
>I have never figured out why specifying a DOCTYPE or having markup that
>could pass validator.w3.org is important to accessibility.
>WAI 1.0 says only this:
> "Validating to a published formal grammar and declaring that validation
> at the beginning of a document lets the user know that the structure of
> the document is sound. It also lets the user agent know where to look for
> semantics if it needs to."
>WAI 2.0 (working draft, April 24, 2002) says this:
> "Checkpoint 5.1 [4.2] Use technologies according to specification.
> You will have successfully met Checkpoint 5.1 at the Minimum Level if:
> except where the site has documented that a specification was violated
> for backward compatibility, the markup has passed validity tests of the
> language (whether it be conforming to a schema, DTD, or other tests
> described in the specification)."
>...All of which boils down to "your documents should validate because we
>say so," which is unsatisfying.
>I understand that specifying a DOCTYPE is important because you can't
>validate without one, and validation is important because validation is
>important, but why is validation important for accessibility? Are there
>user agents that validate a document at rendering time, or that require
>valid documents? Screen readers read broken documents just fine; Lynx
>displays broken documents just fine; invalidity doesn't interfere with
>text zoom or screen magnifiers or any other assistive technology I can
>think of.
>Furthermore, a nested table-based layout and no header tags could be a
>perfectly valid document and still be an inaccessible mess, contradicting
>WAI 1.0's claim that validity implies any measure of structural soundness.
>So why specify a DOCTYPE? Why validate?
>Please CC, I'm on digest.
>-Mark Pilgrim
>To subscribe, unsubscribe, or view list archives,
>visit http://www.webaim.org/discussion/

Jon Gunderson, Ph.D., ATP
Coordinator of Assistive Communication and Information Technology
Division of Rehabilitation - Education Services
College of Applied Life Studies
University of Illinois at Urbana/Champaign
1207 S. Oak Street, Champaign, IL 61820

Voice: (217) 244-5870
Fax: (217) 333-0248


WWW: http://www.staff.uiuc.edu/~jongund
WWW: http://www.w3.org/wai/ua

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