W3C home > Mailing lists > Public > w3c-wai-gl@w3.org > January to March 2002

Re: ems versus pixels

From: Charles McCathieNevile <charles@w3.org>
Date: Tue, 1 Jan 2002 08:46:01 -0500 (EST)
To: Rowan Smith <rowan@absolutely.co.nz>
cc: <w3c-wai-gl@w3.org>
Message-ID: <Pine.LNX.4.30.0201010841490.11629-100000@tux.w3.org>
Well, the accessibility downside depends on what you are soing with your
layers. If you are going to have text positioning determined by them, and
people changing text sizes or window sizes to suit their needs is going to
make a big mess, then the accessibility downside is that the design (not just
using pixels, which is really a fairly small part) isn't going to work. In
this case I would suggest changing the design to start with, to one where it
does work to specify sizes in em units.

If you are trying to put a pretty border around the edge of a page, or place
a picture that doesn't scale properly anyway, then there is probably no real
problem that could be solved by switching to em units.

As I undertstand it the techniques document, where you have obviously looked,
is a FAQ, and raising further issues on it means that there is a need for
some more material there.

Cheers

Charles

On Tue, 1 Jan 2002, Rowan Smith wrote:

  Hi there

  WAI Priority 3 guidelines (WCAG Checkpoint 3.4) recommend using relative
  units rather than absolute. The Techniques document suggests that using ems
  rather than pixels as a unit is a way of doing this even when using absolute
  positioning.

  OK, I can understand that for text specifications like font sizes and line
  heights, but does it apply to positioning layers on a page using CSS? Is
  there an accessibility downside of positioning layers (div tags) by using
  px?

  Thanks

  Rowan


-- 
Charles McCathieNevile    http://www.w3.org/People/Charles  phone: +61 409 134 136
W3C Web Accessibility Initiative     http://www.w3.org/WAI    fax: +1 617 258 5999
Location: 21 Mitchell street FOOTSCRAY Vic 3011, Australia
(or W3C INRIA, Route des Lucioles, BP 93, 06902 Sophia Antipolis Cedex, France)
Received on Tuesday, 1 January 2002 08:46:04 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:47:18 GMT