Appendix A: Glossary of Terms


Accessibility Task Force (ATF)
A subgroup of the Web Standards Project (WaSP) focusing on accessibility, assistive technology, and standards support.
See Americans with Disabilities Act.
A combination of technologies that allows bits of a web page to be refreshed from the server without refreshing the whole page, which gives the user a more responsive, seamless experience. It is a good buzzword, but a lousy acronym for Asynchronous JavaScript and XML (because it doesn' t require XML). Ajax currently is most often seen in Google Maps, Google' s Gmail, and the like. Many accessibility problems have yet to be addressed. A similar result, without using JavaScript, may be achieved using Flash or even HTML frames.

A generic term describing descriptive text attached to certain objects on a web page that can be read aloud by a screen reader, so that a person with a visual impairment can know the nature of such objects, too. Alt-text is therefore an accessible alternative to a potentially inaccessible item of content. For example, the object element may use text embedded within it as a fallback mechanism.

The most common alternative text is found as an attribute of the <img> element, and it describes the function of an image, or is blank in the case of purely decorative images.

It is evil and wrong to refer to this as an alt tag (there is no alt element in (X)HTML), and many hope that WCAG 3.0 will mandate the death penalty for such incorrect nomenclature.

Americans with Disabilities Act (ADA)
A U.S. law passed in 1990 that prohibits discrimination against people with disabilities.
A Java program or application that provides interactivity not offered by (X)HTML and designed to be embedded in, and invoked from, a web page. In many cases, Flash has superseded applets as the means to achieve extra interactivity.
assistive technology
Equipment or software that assists people with disabilities in performing everyday activities. Examples include screen readers and voice-input software.
See Authoring Tools Accessibility Guidelines.
See Accessibility Task Force.
Authoring Tools Accessibility Guidelines (ATAG)
Published by the W3C in 2000 to assist authoring tool developers in "designing authoring tools that produce accessible Web content and to assist developers in creating an accessible authoring interface" ( In other words, your blogging tool or CMS should not only produce accessible pages, but also be accessible itself so that users with disabilities can create content.


In WCAG 2.0, a set of technologies assumed to be supported by, and enabled in, user agents in order for web content to conform to WCAG 2.0. Some examples of entities that may set baselines include authors, companies, customers, and government entities.

A free website accessibility assessment tool developed by CAST, and then acquired by Watchfire. The free version of Bobby was discontinued in April 2003.

Bobby had some utility in checking for things like missing alt-text, but, unfortunately, it lulled site owners into a false sense of security, as they believed that "passing Bobby" guaranteed accessibility. There are many other online "validators," such as Cynthia Says and the WAVE. Gez Lemon has a salutary article about the usefulness of such programs.

The software on a computer that allows websites to be rendered so they can be displayed to users. There are two types of visual browsers. Internet Explorer, Firefox, Opera, Safari, and the like render all content including the latest technologies. Others, like Lynx, are text-only. But many other types of browsers exist, some of which produce voice output, such as IBM Home Page Reader.


Cascading Style Sheets (CSS)
A means of applying styling/formatting to markup (for example, XML or HTML). This has many advantages over using HTML formatting tags, such as <b> and <font>. For a start, CSS formatting is more powerful and allows more flexibility. If you want to change a style, you need only change its definition in the style sheet, rather than changing every instance of it in the HTML. CSS has great uses for accessibility. For example, you can use an alternative style sheet to make the text on a website bigger for the benefit of people with visual impairments. See Chapter 9 of this book for more details.
See content management system.
content management system (CMS)
A program that allows users to create and manage web pages and other content. CMSs are often browser-based. They can range from free blogging tools, such as WordPress, to expensive systems that can run a whole enterprise site, such as TeamSite or Vignette. They are generally template-driven and promise (with varying success) to turn user' s text-based input into HTML. Many spit out horribly inaccessible code, and most do not conform to ATAG and are therefore unable to be used by people with disabilities to produce sites. It' s always important to ask vendors about their conformance to ATAG before purchasing a CMS.
See Cascading Style Sheets.


See Disability Discrimination Act.
design for all
See universal design.
Disability Discrimination Act (DDA)
A name shared by two laws passed in Australia (1992) and the United Kingdom (1995, extended 2005). They both prohibit discrimination against people with disabilities.
A link that takes the form of a capital D near an image. It provides a longer description of the image or its purpose than is feasible using the alt attribute. It' s basically a hack, because most browsers don' t cope with longdesc well.
Document Object Model (DOM)
A view of a document (HTML, XHTML, or XML) that can be parsed and manipulated to add new content, amend styles, and change behavior after a web page has loaded—generally via JavaScript, as this is built into most browsers. See Chapter 10 of this book for more details.
Document Type Definition (DTD)
A file that defines the relationships and constraints for elements and attributes used in the markup language in the form of a schema. For example, a DTD may define whether an attribute is required for a particular element. Effectively, it' s the grammatical rules for the language.
See Document Object Model.
See Document Type Definition.
A language-based learning disability that is often characterized by difficulties with understanding written language and being more attuned to a graphical or an object-based learning style.


The standardized version of JavaScript (JScript in Internet Explorer) that can be used usefully to manipulate the DOM, validate forms, and control Ajax, or uselessly to produce effects such as pictures of unicorns following the mouse pointer. ActionScript (found in Adobe' s Flash) is also a flavor of ECMAScript (and is equally good with unicorns).
Extensible Hypertext Markup Language (XHTML)

Defined by the W3C as "a reformulation of the three HTML4 document types as applications of XML 1.0. It is intended to be used as a language for content that is both XML-conforming and, if some simple guidelines are followed, operates in HTML4 conforming user agents" (

XHTML is very much like HTML with a few extra rules. There are three main flavors. XHTML 1.0 Transitional allows many deprecated tags, and as the name suggests, was designed to help developers make the transition from HTML. XHTML 1.0 Frameset allows frames and therefore has attendant accessibility issues. XHTML 1.0 Strict is, well, strict (when compared with traditional HTML).

The idea that XHTML is "better" than HTML is subject to ferocious (but rather futile) debate, as it is largely a matter of personal preference, understanding the difference, and using the right tools for the job.

Extensible Markup Language (XML)
A language specification from the W3C that allows users to develop their own markup languages (often called vocabularies), and format their documents using style sheets to be presented on a browser if desired. XML has a very strict set of rules that must be adhered to, allowing a lot of control over document format. XML is most useful, however, as a completely language/platform-agnostic data format.
Extensible Stylesheet Language (XSL)
A W3C specification that contains three parts: Extensible Stylesheet Language Transformations (XSLT) for changing the formatting and structure of markup according to a set of rules, Extensible Stylesheet Language Formatting Objects (XSL-FO) for applying a strong set of rules to a document to ensure reliable formatting when printed, and XPath to select the elements required by XSLT.


An open source browser available for all main operating systems, developed by the Mozilla Corporation. The good (but not perfect) standards support and availability of community-written extensions makes it the browser of choice for many web developers.
The name given to the product by Adobe (formerly Macromedia) that allows moving graphics to be displayed in a web page. It refers to the Flash Player, which plugs in to the browser, as well as (more generally) the program and effects. Flash can be made accessible on Windows machines via MSAA, and some of the most widespread screen readers can access the content. Although Flash has gotten bad press from some accessibility advocates, it has proved very helpful in delivering accessible content to people with cognitive disabilities.
A product from Adobe (formerly Macromedia) that allows a developer to create a rich, interactive web page that can update with the server in real time, with Ajax-like results.
A feature of (X)HTML that allows a web author to divide a page into two or more separate windows. If the frame does not have a <title> element, or the <title> element is not meaningful, this can cause accessibility issues. In addition, some browsers do not support frames.


See Hypertext Markup Language.
Hypertext Markup Language (HTML)
The markup language that is used to create the vast majority of web pages. The standards for HTML are controlled by the W3C.


image map

An area of an image on a web page that has links to other areas of the Web. For example, an image map could take the form of a map of Europe, in which clicking the map of England could open a page about warm beer, rain, and world-renown cuisine; whereas the area corresponding to Belgium takes you to a page about great beer and a list of household names in all fields of human endeavor.

There are two types of image maps: client-side and server-side. In Chapter 7 of this book, you will read "If you want to use an image map, make it a client-side image map." A List Apart has a good article on building an accessible, standards-compliant image map.


An object-oriented programming language developed by Sun Microsystems. Java was specifically designed for the distributed environment of the Web and can be used to create applications that can run on a single computer or distributed among several computers in a network. It can also be used to write applets (small, stand-alone programs) or animations, although Flash is more commonly used for these.
A scripting language often used on web pages. It' s a type of ECMAScript. See Chapter 10 for a discussion of JavaScript and accessibility.
The Microsoft variant of JavaScript found in Internet Explorer web browsers.



The process of removing the cellular structure from a layout table and checking the cells' contents in their linear (source) order, left to right, top to bottom. Linearization takes the contents of row 1 column 1, then row 1 column 2, and so on. If any cells contain a nested table, all of those cells are linearized before proceeding to the next cell of the original table. The Lynx browser or Web Developer plug-in for Firefox is a good way to see the linearized structure. See Chapter 6 for a full discussion of how table linearization works.

The purpose of linearization is to see if the content still makes sense, as the linearized order is the order in which a screen reader will voice the web page to the user. If it does still make sense (and it generally does), both WCAG 1.0 and 2.0 say your layout is accessible. But no one has professionally used tables to lay out web pages since Mozart fell off his penny-farthing during a stegosaurus hunt.

A text-only browser that was popular among UNIX users and sometimes used by people with disabilities and those in low-bandwidth areas. Lynx can be downloaded from A Lynx emulator is also available at, and it useful for testing how tables linearize.


Microsoft Active Accessibility (MSAA)
A layer in all modern Windows systems that allows assistive technologies to hook into applications. It is how screen readers "know" what is on the screen.
See Microsoft Active Accessibility.
Using a computer to present multiple types of media simultaneously, in an integrated manner. Media can include sound, graphics, video, text, animation, or any other form of information representation. For the purposes of WCAG 2.0, multimedia refers to combined audio and video presentations, as well as audio-only and video-only presentations that include interaction.


on-screen keyboard
A keyboard that appears on the screen. Users who cannot use their hands can use assistive technology (such as a head pointer) to enter keyboard input via the on-screen keyboard.
In WCAG 2.0, refers to the determination of the application of a process. What were the results of the application of a specific guideline? Were the success criteria achieved?


PAS 78
The Publicly Available Specification from the British Standards Institution (BSI), titled "Guide to Good Practice in Commissioning Accessible Websites," released in March 2006. See Appendix C of this book for more details.
See Portable Document Format.
A module (either hardware or software) that adds a special feature to a larger system or program; for example, a program to play movies on a browser or the plug-in that allows browsers to display Flash content.
Portable Document Format (PDF)
Developed by Adobe Systems Inc., as a way to publish documents electronically, with good formatting for printing and document security (documents are generally read-only). Originally, it was in an image format, and this presented major accessibility issues. Recently, however, Adobe has made large strides in making the PDF format accessible to people with disabilities, although it' s generally more complex to navigate a PDF file or to make a PDF file accessible than doing so with an equivalent HTML document. See Chapter 12 of this book for details on PDF accessibility.
programmatically determined
In WCAG 2.0, means something can be recognized by user agents, including assistive technologies, that support the technologies in the chosen baseline. For our purposes, it seems to mean marking up documents semantically, so a program (like a JavaScript favelet, screen reader, or search bot) can tell what' s a list, what' s a heading, and so on, without having to rely on context.


refreshable Braille display
An assistive device thatturns information into raised Braille characters electromechanically, by raising small pins up through holes in a plate, which can be sensed by users placing their fingers on the plate.


Scalable Vector Graphics (SVG)
A language for vector graphics coded in XML. XML documents can have these graphics placed directly into the document, with many advantages. SVG produces graphics that are smaller, transmit more quickly, are scalable without loss of resolution, can have searchable text labels, and can be interactive. SVG is being developed by the W3C.
In WCAG 2.0, refers to limiting conformance claims to pertain to only some parts of a website. Scoping allows authors to claim conformance to WCAG 2.0 for all URLs in one part of a site and exclude other parts of the site. "Scoping cannot exclude a particular type of content (for example, images or scripts) since it would allow exclusion of individual success criteria" (
screen magnifier
A device (or software) that will make images and text on a screen larger for the benefit of visually impaired users. Many Microsoft Windows machines have a simple screen magnifier built in (available from the Start > Programs > Accessories > Accessibility menu).
screen reader
A computer program that reads the screen to a user. It can be used to surf the Web, to write a spreadsheet or document, or just to read pages. It is closely related to voice output. In many ways, screen reader is a misnomer; most modern screen readers actually read the text in source-code order, regardless of the positions of the various elements in the visual layout. Examples of screen readers are JAWS for Windows, Window-Eyes, and VoiceOver on Mac OS X version 10.4.
Section 508
A common name for Section 508 of the Rehabilitation Act. This is an amendment to a U.S. law that basically says all electronic and information technology purchased or developed by the U.S. government must be accessible to people with disabilities. See Appendix B for details.
See Synchronized Multimedia Integration Language.
spacer image
Small, transparent image placed on a page, usually in a table-based layout, also called spacer GIF. Spacer images are an old-fashioned way to position text and images on the page for a good visual effect. These should be found in only legacy pages, and should have null alt-text (alt="").
style guide
A document that sets out the rules for your website. All your developers must follow your style guide, and the webmaster should enforce it. Accessibility rules and standards can be included in this style guide. This is a good idea, as when a style guide is implemented, accessibility becomes part of the basic parameters for your website and becomes much less of an issue.
style sheet
See Cascading Style Sheets and Extensible Stylesheet Language.
success criteria
In WCAG 2.0, testable statements that will be either true or false when applied to specific web content.
See Scalable Vector Graphics.
Synchronized Accessible Media Interchange (SAMI)
An HTML-like language used to embed captions in Windows Media files.
Synchronized Multimedia Integration Language (SMIL)
A markup language developed by the W3C that allows developers to separate multimedia content into distinct files and transmission streams such as text, images, audio, and video. These can then be sent to the user' s computer separately, reassembled, and displayed as intended. SMIL 2.1 became a recommendation in December 2005.


table linearization
See linearization.
text equivalent
A term used to describe the technique of providing a text alternative that will be the same in both content and function as a nontext object on a web page, such as an image map.
text-only browser
A browser that does not show images. It does not have images turned off; rather, it just doesn' t display them. An example of a text-only browser is Lynx.


See user-centered design.
universal access
The idea that all things on the Internet should be accessible by the largest audience possible, regardless of disability, location, device, or speed of connection to the Internet. It therefore differs from accessibility, which is solely concerned with access for people with disabilities.
universal design
Designing for the largest audience possible, regardless of disability or ability to speak the native language. This is a process rather than an end in itself.
The idea that a website or web page is easily used by a web user.
user agent
A term used by the W3C as a generic description for "any software that retrieves and renders Web content for users" ( A browser, mobile phone, screen reader, plug-in, or search engine' s web crawler may be considered a user agent.
User Agent Accessibility Guidelines (UUAG)
A document that provides guidelines for designing accessible user agents (browsers, assistive technologies, media players, and the like), published by the W3C in 2002. See for more information.
user-centered design (UCD)
The design process that places the user at the center of the design rather than the object to be designed. It is a philosophy and process rather than an end in itself.
See User Agent Accessibility Guidelines.


voice input
Software that recognizes voice commands and responds accordingly.
voice output
Software that reads the necessary information to the user, in a synthesized voice.
voice recognition software
Software that can be trained to recognize a person' s voice and either execute commands or turn the voice into text or other forms of media, such as sign language for the deaf.
A type of XML that allows the user to interact with a web page using voice recognition software.
voicing browser
A browser that uses a synthesized voice as a means to communicate with the user. IBM Home Page Reader is an example. It differs from a screen reader in that a voicing browser is purely a web browser, whereas a screen reader reads any screen.


See World Wide Web Consortium.
See Web Accessibility Initiative.
See Web Standards Project.
See Web Accessibility Tools Consortium.
See Web Content Accessibility Guidelines.
Web Accessibility Initiative (WAI)
Started by the W3C and its members, an organization that addresses web accessibility issues. See for more information.
Web Accessibility Tools Consortium (WAT-C)
Described as a consortium that "provides a collection of free tools to assist both developers and designers in the development and testing of accessible web content." See for more information.
Web Content Accessibility Guidelines (WCAG)
Guidelines developed by the W3C/WAI to address issues in building accessible web pages. WCAG 1.0 was published as long ago as 1999; WCAG 2.0 is "coming soon."
Web Standards Project (WaSP)
Described as a project that "was formed in 1998 with the goal of promoting core web standards and encouraging browser makers to do the same, thereby ensuring simple, affordable access for all." See for more information.
World Wide Web Consortium (W3C)
An international consortium of companies and organizations involved with the Internet and the World Wide Web, responsible for maintaining web technology standards, such as HTML and CSS. See for more information.


See Extensible Hypertext Markup Language.
See Extensible Markup Language.
See Extensible Stylesheet Language.