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Low Vision and CSS (The EM is not enough)

From: Leonard R. Kasday <kasday@acm.org>
Date: Wed, 03 May 2000 14:04:14 -0400
Message-Id: <4.3.1.2.20000503115907.00c97be0@pop3.concentric.net>
To: w3c-wai-gl@w3.org
Cc: w3c-wai-er-ig@w3.org
To WCAG
Copied to ER

People with low vision often increase the default font size.  One might 
think this could be accommodated by using em units instead of absolute 
units, but that doesn't appear to be the case.  If you look at

http://astro.temple.edu/~kasday/wai/css-em.html

using Internet Explorer 5, with medium font size, and a window 
approximately a screen width, you'll see a paragraph at the top and text 
below it.  The lower text is positioned with respect to the window with 
ems.  However, if you now make the window smaller, you'll see the text in 
the top paragraph wrap, causing the number of lines to increase and it will 
eventually overlap the text below it.

Similarly, if you make the font bigger using View->font size, you'll again 
get the overlap.

The moral is that, checkpoint 3.4 to use relative units such as the EM is 
not enough.  There needs to be a more general guideline that pages shall 
read sensibly when default font is made larger.

For convenience, I've included the text of the referenced example in this 
email.

Len

p.s.
Presently, this example works only in MSIE 5, not Opera 3.62 or Netscape 
4.7.  I think MSIE is doing it right.  CSS gurus please check...

==========

This shows that text can overlap even when using ems. If you make screen 
narrower or font larger the text will overlap... at least in Microsoft 
Internet Explorer 5.0 (Overlap does not occur in Opera 3.62, and Netscape 
Communicator doesn't show it at all).
This sentence starts out below the first one.

Len Kasday, kasday@acm.org, Pennsylvania's Initiative on Assistive 
Technology, a program of the Institute on Disabilities/UAP at Temple 
University
--
Leonard R. Kasday, Ph.D.
Institute on Disabilities/UAP, and
Department of Electrical Engineering
Temple University
423 Ritter Annex, Philadelphia, PA 19122

kasday@acm.org
http://astro.temple.edu/~kasday

(215) 204-2247 (voice)
(800) 750-7428 (TTY)
Received on Wednesday, 3 May 2000 14:03:41 GMT

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