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RE: Fixed font-sizes and WAI or 508


From: Jukka K. Korpela
Date: Feb 2, 2004 5:11AM

On Mon, 2 Feb 2004, Mark Magennis wrote:

> Isn't this covered by WAI checkpoint 3.4 which states "Use relative rather
> than absolute units in markup language attribute values and style sheet
> property values"? Font size is an attribute value and a fixed size is an
> absolute unit.

You are quite right. I'm very happy to stand corrected. (Technically, the
Uppsala site uses the font-size property in CSS and not the size attribute
in a font tag, but the checkpoint refers to properties as well.)

I guess I missed it since it's under "Guideline 3. Use markup and style
sheets and do so properly.", which is natural in retrospect, in a sense.
But I wrongly remembered that the guideline only discusses proper use HTML
and CSS in the sense of using the according to specifications, both
syntactically and semantically.

On a finer point, 3.4 says: "For example, in CSS, use 'em' or percentage
lengths rather than 'pt' or 'cm', which are absolute units." Interestingly
it does not mention 'px' in the example, despite the fact that 'px' is
probably the most commonly used unit in CSS. Surprisingly, many people say
that 'px' is a relative unit, and in a sense it is relative to

But the techniques document http://www.w3.org/TR/WCAG10-CSS-TECHS/#units
says: "Only use absolute length units when the physical characteristics of
the output medium are known, such as bitmap images." I'm not sure I see
what this really refers to, but surely the only unit that makes sense for
a bitmap image is 'px', since such an image is inherently a matrix of
pixels. Thus, the 'px' unit is implicitly declared as absolute.
We could rest our case, if WCAG 1.0 had legal and enforceable power. :-)

Jukka "Yucca" Korpela, http://www.cs.tut.fi/~jkorpela/

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