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A Web Accessibility Evaluation And Repair Tool With Application To Section 508 Standards

Leonard R. Kasday
Institute on Disabilities/UAP at Temple University, Philadelphia PA 08057
Email: kasday@acm.org


In practice, most tests of web page accessibility require human judgment.  The WAVE is a tool that helps users apply that judgment, by displaying textual alternatives next to non-textual objects, numbering the reading order, showing where logical tags occur, aiding other judgmental tests, and performing automated tests were possible.  This paper describes the WAVE and a version being adapted to support  regulations implementing Section 508 of the Rehabilitation Act.


It's critical that Web sites be accessible to people with disabilities. Web Accessibility Content Guidelines have been published by the W3C Web Accessibility Initiative (WAI), and legal requirements are being established.  In the United States,  the Access Board has issued aNotice of Proposed Rulemaking (NPRM) on Standards for Electronic and Information Technology, implementing Section 508 of the Rehabilitation Act.  The NPRM is a proposal for rules which will, among other things, require accessibility of web sites used by Federal Employees and members of the public seeking information and services from the Federal Government (see the NPRM for specific requirements and exceptions to the proposed rules). Furthermore, according to a NIDRR Letter on Assurances, all states that receive ATAct funding need to comply with these requirements.

Tools for evaluation and repair of web page accessibility are available and under development. The WAI Evaluation and Repair Tool Interest Group is creating a document describing techniques for evaluation and repair.

One such accessibility tool is the WAVE (Web Accessibility Versatile Evaluator), a web-based service currently available at http://www.temple.edu/inst_disabilities/piat/wave/ .  This paper describes features of the WAVE now available, and features under development, that will specifically help users evaluate and repair web sites according to the rules implementing Section 508.  

Note: as this paper is being written, only the proposed rules in the NPRM are available.  The WAVE will  implement the final rules when they become available.  Meanwhile, some tests not in the NPRM that may be in the final rules (e.g. reading order; see below) are being implemented.

Importance of Human Judgment  and Context

One would like to evaluate web accessibility in a fully automatic manner analogous to how the  W3C HTML Validator checks HTML validity.  However, most accessibility checks require human judgment.  Furthermore, when judgment is applied to an HTML element, the surrounding context of that element must be taken into consideration.  Here are some examples.

ALT Text.

The 508 NPRM requires all images to have an alternative textual equivalent, e.g. "ALT text", a (usually invisible) textual equivalent of an image that a person who is blind will be able to access via speech or Braille using web browsers that have speech built in or that are used with screenreaders. An automated tool can check if ALT text exists, but cannot tell if the ALT text is correct.  For example, a button labeled "YES" could have alt text "NO", and if the text is too stylized to be read by optical character recognition (OCR), this error cannot be detected (also,  currently available evaluation tools don't use OCR, and thus would not detect this error in any case).  

For images that are not text, context must be considered.  Consider, for example, this image of a lightbulb Cartoon image of lightbulb from  New Zealands Ministry of the Environment.    It's used as a decorative element next to the textual label "energy" and  the ALT text is, appropriately, set to the null value (ALT=""). If it were not accompanied by a textual label, e.g. as a marker icon in a table items, appropriate ALT text might be "lightbulb", "lighting item", "new product idea", "brighten", etc.    Similarly, for larger images, judgment is need to determine if ALT text should be null, a word or two of description, or a more extended description; and whether any longer description should appear as ALT text or elsewhere, e.g. a LONGDESC reference, or in the body of the document.

Thus, human judgment is required to evaluate ALT text for images, and the context of the images must be considered.

Reading Order.

The 508 NPRM requires that pages be readable without any accompanying style sheets.  Style sheets (among other things) can position elements in a visual order different than what a person using a screenreader would hear.  Human judgment is needed to determine if the screenreader reading order makes sense. Reading should also be checked when tables are used for page layout (this is not explicit in the 508 NPRM, but is required by the W3C guidelines referred to earlier, and recommendations for adding the reading order requirement have been made in public comments).

For example, in most browsers, a sighted person reading the boxed text below will read "This guidelines is priority two" (the text may slope upwards at a slight angle).


However, a blind person using a screenreader that has " linearized" the web page,  (e.g. Lynx or JAWS after the F5 reformat key is pressed) will hear  the words backwards, i.e. "two priority is guideline This". The linearized reading order is backwards because  the text is laid out in a table and some cells span two or more rows.  If the table borders are made visible and the cells are numbered in reading order it looks like this:

arrow: 1
arrow: 2 arrow: 3 arrow: 4 arrow: 5 arrow: 6 two.
arrow: 7 arrow: 8 arrow: 9 arrow:10 priority
arrow: 11 arrow: 12 arrow:13 is
arrow: 14 arrow:15 guideline
arrow: 16 This

The backwards reading order is a result of reading the table one row at a time.

This example is made extreme to illustrate the importance of reading order, but there can be reading order problems in realistic web pages. 


Example of use

The WAVE is a tool that helps a person determine if a web page is accessible.  Except for special cases, the WAVE itself does not determine that there is an error.  Instead, it gives the user the information he or she needs to apply the judgment needed to determine accessibility. (Note that by "user" I mean the person evaluating accessibility, not a person actually using the site).  Some of the current features of the WAVE are shown in the following example of a fictional government web site.

Screenshot of web page with image of large checkmark and an image of person at a computer. There's a bullet list with three items. Also an image map with an eagle, title 'Sample Government Web Site', and items Mission, Service, and Contact. There's a text link called 'Welcome'. Plus a form with three text fields, with labels name, address, and email above the fields.

The output of the WAVE is as follows:

Screenshot which is described in the text of this paper.

The WAVE output is labeled by icons that help the user see a number of errors that (except where noted) violate 508 NPRM requirements .  Note that except for missing ALT text, WAVE doesn't determine that there is an error: it gives the user the information he or she needs to determine whether there is an error:

  1. The image of the checkmark has no ALT text, as shown by the missing alt text. .  This check is fully automatic.
  2. The ALT text icon ALT text"Shopping Adventure Main Menu" shows the user that the ALT text is "Shopping Adventure Main menu".  The user immediately realizes this ALT text is wrong. The ALT text should have been e.g. ALT text"Sample Government Web Site Main Menu".  Similarly, the user sees that  the first two buttons in the image map have reasonable ALT text, but the third is ALT text"Bottom button" which is another error since it isn't a useful equivalent for the  "contact" button.
  3. The icon suspicious alt text.shows that the ALT text for the image of the person at a pc, "desk_pc.gif (4618 bytes)" is suspicious.
  4. The WAVE spots that the "Welcome" link is an audio file and asks if there is a text equivalent.
  5. The arrows and numbers (e.g. .arrow icon  1, .arrow icon  2, .arrow icon  3, etc) indicate the order in which parts of the page are read, revealing that in the form all the labels  are read (name, address, and email) before the user reaches the fields.  The user realizes this is poor reading order: it should have been designed to read: name, FIELD, address, FIELD, email, FIELD.   (As noted above, comments on the NPRM include a recommendation to add this requirement to the final rules).
  6. The icons Heading 1. , Heading 2., etc. show that elements are truly tagged as level 1 headings, level 2 headings, etc. The bullet listicon shows that what follows  it is a true bullet list.  Thus the user can judge if the document structure is correctly communicated without stylesheets (or FONT tags, or other HTML that merely imitates appearance--although that's not required by the NPRM).  However, these marking show that the title "Our Cyber-services" is labeled with a "strong emphasis" tag Strong Emphasis..  The user might judge H2 to be more appropriate.

As explained above, most of these checks require human judgment.  The WAVE focuses on helping users apply that judgment quickly and efficiently (in addition to performing automatic checks where possible).

Section 508 Accessibility Evaluation

A version of the WAVE is being adapted specifically to support the 508 regulations.  The 508 NPRM contains 13 specific Web Accessibility requirements (a number which may change when the final rules are issued).  The WAVE will provide a checklist of the requirements with links to specific instructions for checking the requirement with the wave, and links to the relevant WAVE features. For example,.

Requirement Check
  1. A text equivalent for every non-text element shall be provided via "alt" (alternative text attribute), "longdesc" (long description tag), or in element content. ALT text iconSuspicious ALT text icona red missing alt text icon.blank alt text.:


In the actual checklist, clicking on the icons under "Check" will access instructions on using the checks, viz those checks that can produce the corresonding icon.  The WAVE will also give the user the option of running tests in subgroups to reduce the complexity of the display.

ALT Text Editing

The WAVE also allows "repair" of ALT text.  Instead of only displaying the ALT text, the WAVE can optionally present the ALT text in a field, e.g.

ALT text icon

If the user types new ALT  text, then pressing a SUBMIT button will generate a new page with the corrected ALT text.

Development Status

As of the date of submission of this paper (2 October 2000) the WAVE runs the ALT text checks described above,  shows reading order, displays equivalent for applets, warns of elements tied to Javascript, shows logical structure tags (headings, lists, emphasis), warns when links point to audio files, and shows keyboard shortcuts (access keys).  It processes web pages via a web-based form or via a button that can be added to Netscape or Microsoft browsers.  It handles frames and Secure Sockets Layers (SSL).  The basic ALT text Editing feature has been implemented, (although it's not yet available on the public web form).

These checks cover 5 of the 13 requirements in the NPRM  proposed rules in whole or part.  Most or all support will be available by the CSUN 2001 meeting (March 2001), assuming the final Access Board rules do not differ greatly from those in the NPRM.


The initial motivation for the WAVE was to help users efficiently apply the human judgment inherently required for most tests of web accessibility. In response to user requests, the WAVE is being enhanced to add tests, the repair of accessibility problems, and specifically aid application of standards such as the regulations implementing Section 508 of the Rehabilitation Act. Users will also be able to use the WAVE to check additional requirements, such as those recommended by W3C.


The WAVE is being developed with support from grant H224A20006-99 from the Department of Education.  The author is very grateful for all the advice and feedback he's received from members of the W3C Web Accessibility Initiative Evaluation and Repair Tools Group, and other users of the WAVE.


All references are included as hyperlinks in the body of this document.

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