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Re-post: Influence of valid code on screen readers

From: Joe Clark <joeclark@joeclark.org>
Date: Mon, 13 Jun 2005 20:33:34 +0000 (UTC)
To: WAI-GL <w3c-wai-gl@w3.org>
Message-ID: <Pine.LNX.4.60.0506132028410.31349@aristotle.multipattern.com>

Another action item (though it didn't make it onto the list of action 
items) from a couple of phone calls ago asked me to re-forward to the list 
the evidence from two screen-reader manufacturers about the importance of 
valid HTML.

Both said it was important. The issue is the complexity of the document 
tree in tag-soup HTML, as explained separately by Ian Hickson:

<http://ln.hixie.ch/?start=1037910467&count=1>


This was on the list before:

<http://lists.w3.org/Archives/Public/w3c-wai-gl/2004JanMar/0189.html>

and is also on my personal Weblog:

<http://blog.fawny.org/2004/05/13/screen-reader-code/>


And it reads as follows:


Do screen readers work better with valid HTML?

    The answer is yes.

[15]Is validity an accessibility issue?

      The need to use technologies according to specification is a
      broader issue than most of the guidelines in WCAG. In issue 572 as
      well as on the mailinglist, people have wondered whether this
      guideline should be in WCAG because they feel it's not about
      accessibility. Others have argued that valid markup increases the
      chances of correct rendering of the content which directly benefits
      accessibility.

      I canvassed the makers of Two Leading Screen Readers. Take a wild
      guess as to which two.

      [INS: [Product 1] :INS] does tend to behave better with valid code
      because the browser behaves better with valid code. Take, for
      example, tables. Invalid table code may cause tables to be rendered
      incorrectly, thereby causing [INS: [Product 1] :INS] to read them
      incorrectly. Since we get information about the page directly from
      the DOM, if the DOM is invalid, the information we're presenting to
      the user has the potential to be invalid as well. Ideally, if the
      DOM is correct, we will be correct.

      And:

      The developer who handles the HTML code states that valid HTML is
      very important for screen readers as working around it is one of
      our greatest hassles.

      As for the specific elements and attributes supported by [INS:
      [Product 2] :INS] , I will have a comprehensive list available by
      mid-February. Our documentation team is working on some training
      materials for making accessible web sites and this will be a
      portion of their effort.

    (Still waiting for that one. I sent in another request.)
Received on Monday, 13 June 2005 20:33:50 UTC

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