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Re: note from Prof Knuth

From: L. David Baron <dbaron@dbaron.org>
Date: Tue, 20 Sep 2005 23:39:45 -0700
To: mam@theory.Stanford.EDU, www-validator@w3.org
Message-ID: <20050921063945.GA16765@ridley.dbaron.org>
On Wednesday 2005-09-21 12:06 +0900, olivier Thereaux wrote:
> On 21 Sep 2005, at 08:24, Maggie McLoughlin wrote:
> >You suggested that I try
> >  valign="middle"
> >in place of
> >  align="absmiddle".
> valign was my mistake, sorry.
> The standard way to do this is:
> style="vertical-align: middle"
> or, better
> class="absmiddle"
> With a rule in your style sheet that sets
> img.absmiddle { vertical-align: middle }

These are actually three different things:

  align="middle" on an HTML img means that the center of the image
  should be vertically aligned with the baseline of the text.

  align="absmiddle" on an HTML img used to mean [1] that the image
  should be centered within the line as a whole (or at least the content
  preceding it on the line, as implemented in Netscape 4.x), but now
  generally means the same thing as CSS 'vertical-align: middle' [2].
  I'm not sure what the behavior in older versions of Internet Explorer
  [1] http://wp.netscape.com/assist/net_sites/html_extensions.html
  [2] http://www.w3.org/TR/html4/struct/objects.html#adef-align-IMG

  CSS vertical-align: middle means that the center of the image should
  be vertically aligned with the middle of the text's x-height.

The bigger question here, though, is whether Web standards are being
designed to support the ability to view documents created today decades
or centuries from now.  Given the rapid production of new standards, the
low level of concern for making them all work together, the versioning
strategies fashionable these days, and the insufficient depth of public
test suite coverage, I think the answer is currently no.


L. David Baron                                <URL: http://dbaron.org/ >
          Technical Lead, Layout & CSS, The Mozilla Foundation

Received on Wednesday, 21 September 2005 06:39:55 UTC

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