WCAG 2 – relative units

I know, it’s late. Very late. However, given the speed the process seems to work at, hopefully not too late.

I added a comment to the WCAG 2 official list over the main missing item from my point of view: relative units.

I didn’t propose to simply bring it back (well, yes for fonts, layouts are a bit more complicated), but it is a big hole in the new version. Here’s my comment:



Item Number


Part of Item

Intent, Description, Examples

Comment Type



I cannot find anything on relative sizing of fonts or layout, at all. (Also noted in other comments.) I believe these are important aspects for accessible computers in general as well as the Internet, for anyone with a mild to moderate visual impairment.

  • The most common user agent Internet Explorer (installed on many corporate networks) does not allow the resizing of pixel sized fonts. Nor does the version 7(b3) update. (It does include ‘zoom’, but this causes horizontal scrolling on any currently accessible site).
  • Proper ‘zooming’ is not generally available yet (although some are working on it.)
  • Fixed width/height layouts suffer from a similar problem, partly because they often do not react well to increases in font size. There are some basic layout guidelines for HTML/CSS websites.
  • It is applicable to all screen technologies. For example, Flash scales well, but is often trapped in a fixed size window. Acrobat has re-flow & scaling. Other new technologies should be required to scale well.

Relative fonts or layout may be covered in the techniques (although not when I last searched), but I believe it should be part of the normative document (level 2 success criteria).

Proposed Change

Include a revised version of WCAG 1.0’s checkpoint 3.4, example included below. The font aspects could be added to 1.3, but it does not seem a natural fit.


Guideline 1.5 Use scalable fonts and layout

Level 1 Success Criteria for Guideline 1.5

(No level 1 success criteria for this guideline.)

Level 2 Success Criteria for Guideline 1.5

1.5.1 text sizing should be specified in a unit that is user re-sizable. The interface should be perceivable and operable with text increased to a 200% size.

1.5.2 the layout of the page should allow for a variety of screen resolutions and sizes by using relative units for the primary layout areas, such as overall layout, and content area.

Somewhat short, rough and ready, but I can expand on this if the concept is agreeable. This article on basic layout guidelines could provide inspiration for the CSS techniques.

End of comment.


One contribution to “WCAG 2 – relative units

  1. Aaah! I thought that comment might have been from you. I commented on your comment in my public sector forums talk, as it were. I never actually thought to check your site to see whether it was you, though…

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