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Re: CSS-P, layers, links and accessibility

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From: Tom Dahm
Date: Jul 25, 2001 9:09AM


Leo,
I'd advise you to stay away from CSS positioning. Netscape 4 doesn't support this reliably enough to make it a safe technology, and NN 4 still makes up about 15% of the browser market.
In general I'd be cautious about full implementation of the WAI guidelines, since they're based on the assumption that all browsers fully support the latest W3C standards.
Even though CSS isn't exactly a new standard, and the latest versions of NN and IE support it well, the presence of old browsers means you can't hang your hat on it yet. There are a lot of other accessibilty tags in the HTML standards that aren't widely supported yet (LABEL is a good example).
That's the main reason for the difference between the 508 requirements and the WAI guidelines. The WAI rules are based on the browser market as it should be; the 508 guidelines are based on the market as it really exists today.
Hope this helps.
Tom Dahm
NetMechanic, Inc.
"Power Tools for Your Web Site"
http://www.netmechanic.com
At 08:55 AM 7/25/01 -0400, you wrote:
Hi everyone,
I had a couple of questions regarding CSS absolute positioning and accessibility that I was hoping someone could clear up for me.
I am hoping to implement CSS-P (absolute positioning or what Dreamweaver calls layers) as much as possible in the site that I am presently redesigning, as I would very much like to get away from using tables for complex layouts.
I have read a good deal of literature about web accessibility and the fact that CSS should be used as much as possible for presentation and layout. The W3C techniques section for checkpoints 3.3 and 5.3 states that: Layout, positioning, layering, and alignment should be done through style sheets (notably by using CSS floats and absolute positioning):'float', 'position', 'top', 'right', 'bottom', 'left'. With these properties, the user can control the visual position of almost any element in a manner independent of where the element appears in the document. Authors should always design documents that make sense without style sheets (i.e., the document should be written in a "logical" order) and then apply style sheets to achieve visual effects.

However, I have found that when using layers, that links contained within them are not accessible via the tab key in Netscape 4x or 6, whether I use the <div> or <span> tag to code the layer.
For example:
<span id="Layer1" style="position:absolute; visibility:visible; z- index:1; left:50px; top:150px; width:100px"><a href="somewhere.htm">link</a></span>
or
<div id="Layer1" style="position:absolute; visibility:visible; z- index:1; left:50px; top:150px; width:100px"><a href="somewhere.htm">link</a></div>
neither of these allow links contained within them to be tabbed to when viewed in these browsers.
I have not read anything in the 508 or W3C guidelines that specifically says all links on a page should be accessible through the tab key, other than W3C Priority 3 specification 9.4 which states "create a logical tab order through links, form controls and objects".
Does the fact that Netscape 4x or 6 browsers do not allow access to links within a layer through the tab key mean that absolute positioning should be avoided?

Also, both the 508 and the W3C guidelines state that a document should be readable when style sheets are turned off.
Am I correct in assuming that inline styles do not come under "style sheet" in this directive?
That is, an inline style such as:
<span style="background-color:#ffffcc">hello everybody</span>
or like the layers above:
<div style="position:absolute; left:10px; top:50px; width:100px">The quick brown fox jumped over the log</div>
would not be included under this style sheet independence directive.

Thanks so much for your time and valuable input.
Best,
Leo.

Leo Smith USM Office of Publications and Marketing 207-780-4774