2006 Conference General Sessions

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MOZILLA/FIREFOX ACCESSIBILITY EXTENSION

 

Presenter(s)
Jon Gunderson
UIUC
1207 S. Oak Street
Champaign IL 61820
Day Phone: 217-244-5870
Fax: 217-33-0248
Email: jongund@uiuc.edu

Presenter #2
Richard Schwerdtfeger
IBM
Austin TX  
Email: schwer@us.ibm.com

The Mozilla/Firefox Accessibility Extension [1] provides navigation, styling and rendering features that are important in improving access to web content for people with disabilities and testing web resources for functional accessibility by developers.

Web browsers play a critical role in web accessibility and their features play a major role in defining the web content

accessibility techniques available to web developers.  The Mozilla/Firefox Accessibility Extension [1] provides navigation,

styling and rendering features that are important in improving access to web content for people with disabilities and testing

web resources for functional accessibility by developers.  The features are based on the W3C User Agent Accessibility

Guidelines [2].  The extension also implements features to support the new Dynamic HTML accessibility features [3] being

developed by the W3C Protocols and Formats group.  

More information at:
http://cita.disability.uiuc.edu/software/mozilla

Mozilla/Firefox Accessibility Extension

The Mozilla/Firefox accessibility extension provides additional features to the Mozilla and Firefox browsers through a

toolbar, menu options and keyboard shortcuts.  The importance of browsers features for web accessibility can be illustrated

through the Section 508 [4] web accessibility requirement of skipping navigation bars.  Web accessibility resources and

e-mail lists associated with web accessibility are clogged with a variety of techniques to implement the “skip navigation”

feature, with many of the techniques not even accessible to the people the requirement was designed to help.  If Internet

Explorer would have a keyboard shortcut for header (H1-H6) navigation built into it, like the Opera browser, there would not

have been all these techniques and people would have been encouraged to use headers for structure.  Instead we got a variety

of techniques that are confusing and often not accessible to people with disabilities, and the use of headers is typically

not mentioned in most of these techniques.

Through implementation of the W3C User Agent Accessibility Guideline [2] requirements the Mozilla/Firefox accessibility

extension serves as a tool to help people with disabilities access web content and allow developers to functionally test

their web resources based on content conforming to the W3C Web Content Accessibility Guidelines [5] and Section 508

guidelines[4].  The extension is also being used as a test platform for the new W3C Dynamic Accessible Web Content Roadmap

[3] being developed by the W3C to improve the accessibility features of web applications.   

Navigation

One of the main problems with popular current browsers like Internet Explorer and Mozilla/Firefox are their limited ability

to navigate the structural elements of HTML.  In the case of Internet Explorer (IE) the structural navigation features have

appeared in assistive technologies like JAWS and WindowEyes screen readers.  If structural navigation features would have

been built into IE then assistive technologies would not have had to create them and then all users would benefit, including

people with disabilities, especially those who do not use screen readers.  Other mainstream browsers like Opera do have some

built-in navigation features like list of links and keyboard header navigation, so not all browser developer shared in the IE

navigation model.

The benefit of the Mozilla/Firefox browsers is their ability of their features to be easily extended using Javascript, XUL

and the Geko Document Object model (DOM).  The extension uses these technologies to add additional navigation and keyboard

features for supporting HTML structural markup. There are two basic types of navigation: sequential navigation using keyboard

short cuts to move keyboard focus to the next and previous structural element in the document and the other is through a

“enumerated list” of the text content associated with the structural element.  For example with header there are keyboard

commands to go to move keyboard focus to the next and previous header elements in a web resource.  There is also a list of

header feature that lists all the headers in a dialog box with the associated heading level, heading text and sequence number

in the document.  The user can then sort the list by document order, heading level or alphabetically by the heading text.  As

the user moves through the list box the corresponding header in the document is synchronously highlighted for the user to see

the header in the context of other content in the resource.  The implementation of the keyboard shortcuts is done in a way

that they can be customized by the user using the configuration features built-in to Mozilla and Firefox.  This allows users

to disable or move functions to other keys if they interfere with assistive technologies or other extensions that they may

want to use.

IMAGE: list-of-headers.png
ALT TEXT: List of headers Dialog Box

Summary of navigation features

• Headers: Next header, previous header, list of headers
• Links: Next link, previous link, list of links
• Forms: Next form control, previous form control, list of form controls
• Navigation bars: Next navigation bar, Previous navigation bar, list of navigation bars
• Fames: List of Frames
• Data tables: List of data tables, cell navigation
• Accesskeys: List of accesskeys

Text Descriptions of Images

The text description options allow users to easily turned images on/off, replaced images with ALT text or to see a list of

all the images.  The list of images option provide a means for developers to easily scan through the images for proper alt

text.  The “Open Long Description” button in the list dialog box allows users to easily access the longdesc URL attribute

when defined by authors to access extended descriptions of images.  The ALT text replacement function goes beyond the

built-in in ALT text rendering built into  Mozilla/Firefox, which typically clips ALT text to the size of the graphical area

assigned to the original image.   Unlike IE there is no override of this clipping feature.  The extension actually creates a

text node in the document object to provide full text styling and zooming capabilities to the ALT text and also does not clip

the text off at the size of the image.

IMAGE: list-of-images.png
ALT TEXT: List of Images Dialog Box

Styling

The styling features allow the user to turn off author stylesheets and inline styling.  Users can also apply their own

stylesheet or turn on/off a built-in high contrast stylesheet.  Users can easily restyle content to their own needs and the

zoom toolbar buttons make the zoom features built-in to Mozilla more visible to users.  Developers can easily use the style

functions to see how their web resources translate to alternative renderings or adapts to users increasing and decreasing

text size.

Dynamic HTML and Automation

The web is rapidly becoming the tool of choice for developing user interfaces to software applications.  The interoperability

of the web provides the opportunity to create software based services that can be used on a wide range of operating systems

and browsers without the user needing to install and configure special software on their local computer.  As web applications

become more dynamic and interactive a new level of accessibility markup is need to be able to semantically identify the

purpose, actions and relationships between elements in the user interface.   The W3C Protocols and Formats working group is

developing a set of W3C Recommendations to address the authoring and browser features needed to make web applications more

accessible[3].

The Mozilla/Firefox extension supports these new specifications and provides a tool that can be used for testing the

specifications for functional accessibility by people with disabilities.  The heart of the new specifications is the use of

the xhtml2::ROLE attribute to assign a semantic label to an element or an element content container(i.e. DIV element).  New

features in the W3C DOM support exporting state and property value information to accessibility APIs like Microsoft Active

Accessibility[6] and the GNOME Accessibility API [7].    

The Mozilla accessibility extension allows users to navigate a document based on role types and to selectivity display

document sections.  Interactive controls can be monitored for their current state and their relationships to other elements

in a web interface.  In addition to sequential navigation through the keyboard and the “Table of Contents” function provide a

list of the elements with role assignments.

IMAGE: table-of-contents.png
ALT TEXT: Table of Content list box

Summary of current and planned features of dynamic html accessibility:

• Sequential navigation of primary and secondary content
• Table of Contents function
• Inclusion of navigation bars in the “List of navigation bars” dialog
• Hierarchical navigation of document structure
• Role and state dialog box monitoring functions
• Auto assignment and user override of keyboard shortcuts

Conclusions

The Mozilla/Firefox accessibility extension provides an accessibility tool that can be shared by both users with disabilities

and developers to access and test the functional accessibility of web resources.  The use of the extension as a test for

dynamic html accessibility will provide important feedback to the W3C Protocols and Formats working group on the functional

accessibility afforded in the “Dynamic Accessible Web Content Roadmap” [3].

References

[1] Mozilla/Firefox accessibility extension, http://cita.disability.uiuc.edu/software/mozilla 

[2] Jacobs, I., Gunderson, J., Hansen, E. (2002) User Agent Accessibility Guidelines 1.0, http://www.w3.org/TR/UAAG/.

[3] Schwerdtfeger, R. (2005) Dynamic Accessible Web Content Roadmap, http://www.w3.org/WAI/PF/roadmap/

[4] Section 508 Electronic Information Technology Accessibility Standards,

http://www.access-board.gov/sec508/standards.htm

[5] Chisholm, W., Vanderheiden, G., Jacobs, I. (2000) W3C Web Content Accessibility Guidelines, http://www.w3.org/TR/WCAG 

[6] Microsoft Active Accessibility Resources,

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnanchor/html/accessibility.asp

[7] GNOME Accessibility API, http://developer.gnome.org/projects/gap/GNOME-Accessibility.html


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