pilot implementation of Error reporting for missing alt

I'm writing to let everybody know that I've added an experimental
implementation of missing-0alt Error-reporting support Error
support in a pilot version a validator.nu-based next-generation
W3C markup-validation service that I have been working on for a
while now.

You can try it here:


Note: If the document you want to validate has an HTML4 or XHTML
to doctype, you will need to click the Options button and then
choose "HTML5" from the "Preset" select menu to cause the
document to be validated as an HTML5 document instance.

There are two Error messages that it reports for cases of missing alt:

  Error: Element img is missing required attribute alt. Consult
  _guidance on providing text alternatives for images_.

  Error: Element figure has descendant element img that is missing
  required attribute alt. Consult _guidance on providing text
  alternatives for images_.

The "guidance on providing text alternatives for images" part is
hyperlinked text, the target for which is currently this page:


As explained on that page, the current expectations of this
implementation are for the content to conform to a set of markup
cases that are the union of the criteria in the "Guidance for
conformance checkers" subsection of the img-element section of the
current HTML5 draft, and the criteria in Laura's "HTML5 Change
Proposal: Replace img Guidance for Conformance Checkers".

Please try it. If you find problems or have comments, please raise
bug reports here:


I suppose the fact that I've taken the time to implement this
could be seen as a reversal of the this-should-be-a-Warning
position I supported during the a11y TF face-to-face. The only
useful thing I can say is that some recent circumstances have led
me to conclude that, in the interest of finding best route to
agreement on this issue in the TF and the HTML WG, coding and
deploying a trial implementation of Error-level reporting for this
seemed to be a better investment of my time than further
investment in attempting to address the objections against the
Warnings proposal. If/when I have more time, I'll maybe try to
write a longer message with some more details about that.


Michael(tm) Smith

Received on Thursday, 15 April 2010 14:26:51 UTC