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Re: X-UA-Compatible meta tag and Assistive Technologies

From: Mark Rogers <mark.rogers@powermapper.com>
Date: Fri, 3 Feb 2017 12:53:28 +0000
To: "tink@tink.uk" <tink@tink.uk>, Herin Hentry <herinhentry@gmail.com>, "w3c-wai-ig@w3.org" <w3c-wai-ig@w3.org>
Message-ID: <3BA0E49D-18B8-478A-8992-40FDDBEE36DE@powermapper.com>
One interaction that affects AT is that IDs become case insensitive in quirks / emulation modes. 

This impacts any accessibility features using IDs: label for, aria-labelledby, aria-describedby, etc

For example, this code only has a working label when used with certain DOCTYPEs or  X-UA-Compatible settings:

<!—mixed case ID reference -->
<label for=”FirstName”>First Name</label>
<!—lowercase ID -->
<input id=”firstname” type=”text” />

Similar problems happens when a page has two IDs  that only differ by case.

Root cause is an apparent contradiction in the HTML 4.0 and 4.01 specs: the normative DTD in the spec says all name tokens (including IDs) are case-insensitive (NAMECASE GENERAL YES). The normative text describing ID in the same spec says it’s case-sensitive. 

This causes weird problems in validation:

- The above example validates if used on a page with an HTML 4.01 doctype (because the IDs are a case-insensitive match)
- The above example doesn’t validate with an XHTML doctype (all name tokens, including IDs, are case-sensitive in XHTML)
- The above example doesn’t validate with the HTML5 validator (which doesn’t use DTDs)


Mark Rogers - mark.rogers@powermapper.com
PowerMapper Software Ltd - www.powermapper.com 
Registered in Scotland No 362274 Quartermile 2 Edinburgh EH3 9GL 

On 02/02/2017, 09:35, "Léonie Watson" <tink@tink.uk> wrote:

    On 02/02/2017 04:10, Herin Hentry wrote:
    > I am working on few applications that re-renders in IE Edge in the
    > Emulation mode (IE 5, 7, 8, 9) as they have the X-UA-Compatible meta tags.
    > Has anyone noticed any issues screen readers or other assistive
    > technologies face due to this?
    >   * Visually there are CSS styling differences between Edge and the
    >     older IE versions
    >   * Deprecated HTML tags are adjusted by the IE version.
    With the exception of text introduced using the before/after selector 
    [1], and focusable content that is reordered using things like FlexBox 
    [2], CSS does not tend to affect screen readers.
    The use of deprecated HTML tags might be a different story. I think it 
    would depend on whether emulation mode changed the way the accessibility 
    tree was constructed, as well as how the content was rendered. Do you 
    have an example you can point to?
    > Has there been any research done in this area to refer to about there
    > interaction with ATs?
    None that I know of, or could find based on a few minutes searching.
    [1] http://tink.uk/accessibility-support-for-css-generated-content/

    [2] http://tink.uk/flexbox-the-keyboard-navigation-disconnect/

    @LeonieWatson tink.uk Carpe diem

Received on Friday, 3 February 2017 12:54:28 UTC

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