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From Citizendium, the Citizens' Compendium
Web Accessibility describes the availability of the content, or meaning, of a website, to visitors of varying abilities and whose website viewing mechanisms may differ from the norm.
The webmaster may take steps to style web pages to prepare for special accessibility needs.
For example, unsighted viewers, rely on screen readers (such as Jaws). Senior website visitors, or others with poor eyesight, may need easily to be able to enlarge the print size, if it is not large enough, already.
Some viewers may be color-blind, and cannot depend upon color as a means of conveying desired website actions. Others may need to navigate a website by keyboard alone, without a mouse.
All these, and other needs, depend upon the webmaster's careful foresight and preparation.
The World Wide Web Consortium (W3C) launched its International Web Accessibility Initiative (WAI) on April 7, 1997. On May 5, 1999, the Web Content Accessibility Guidelines became a W3C recommendation.
In the WAI/WCAG is a description of three levels to which a website may "conform to accessibility". Level I describes rules which must be observed: an example is, providing a text alternative for images, when images cannot be displayed.
Level II describes rules which should be observed. An example is, use header elements in the proper order to convey document document organization (for example, <h1>, <h2>, <h3>, and not, say, <h1>, <h3> (perhaps followed by <h2>). Preferably, all these should convey a document's "tree structure".)
Level III describes rules which may be observed. An example is, "create a logical tab order through links, form controls, and objects." (Aside: !?!)
A group of developers, led by Joe Clark, has also published a website, WCAG Samurai, describing Errata in the WAI/WCAG standards. Notably, the Samurai take issue with the fact that, the WCAG fails to meet its own accessibility standards. Most notably, WAI/WCAG fails the test of clarity.
The onus lies upon the webmaster to care enough to pass an idea.
Standards, guidelines, and suggestions abound.
An exhaustive reference may be found in Web Accessibility: Web Standards and Regulatory Compliance (©2006 by Jim Thatcher et. al., friendsofED/Apress). Here, one may find the laws, case studies, methods, debates, and resources.
The Telecommunications Accessibility Homepage describes the Telecommunications Act of 1996 (Section 255). The Telecommunications Act of 1996, a comprehensive law overhauling regulation of the telecommunications industry, recognizes the importance of access to telecommunications for people with disabilities in the Information Age. Section 255 of the Act requires telecommunications products and services to be accessible to people with disabilities.
Section 508 of the Rehabilitation Act …requires access to electronic and information technology procured by Federal agencies. The Access Board developed accessibility standards for the various technologies covered by the law. These standards have been folded into the Federal government's procurement regulations.
The American Federation for the Blind has published a checklist for website characteristics for sightless access.
The National Institute on Aging/National Library of Medicine has published a checklist for Making your Website Senior Friendly.
First and foremost, an accessible website depends upon clear writing. A webmaster must have a message, be sure someone wants it, and care enough that someone will be able to receive it. Language, both in human terms, and crisp code, is essential.
An accommodation usually provided for unsighted visitors is a "skip navigation" link at the beginning of a page. This is done so that the screen reader need not read through all navigation links before jumping to the essence of content.
To avoid page clutter for sighted visitors, the "skip navigation" link is often styled, via CSS, as an invisible element, with a large negative margin, placing it far to the left, off the screen.
In CSS, the webmaster may specify page measurements in relative measurements instead of absolute. That is, measurements may be specified in ems or percentages or keywords such as larger and smaller, rather than in absolute px. Some browsers have difficulty, when site visitors with limited vision, attempt to enlarge print specified in px.
Webmasters can be sensitive to print/background contrast. Red print on a green background may not be appropriate for various visitors who are color-blind. This is a simple matter of CSS style.
Webmasters may avoid light shows: some forms of epileptic seizures are provoked by such elements.
Webmasters may avoid use of tables, especially for page layout. A screen reader proceeds down the column, then down the next column, and so on. This may give a distorted view of the contents of the table. (Tables are also slow to load. CSS provides much better alternatives.)
Text alternatives for all images (provided via 'alt=') should be considered. Unsighted visitors may otherwise miss essential content.
Though validation by humans is the only true test of a page's accessibility, several automated validators are available to provide an initial sense of accessibility:
- Cynthia Says is a widely used accessibility test, and can report levels WAI/WCAG levels I, II, and III conformance, along with Section 508.
- Fangs is a Firefox add-on, which simulates the screen-reader output of Jaws
- T.A.W.3® is the Web Accessibility Test (TAW stands for Test Accessibilidad Web, but the site is in English.)
- Watchfire WEBXACT analyzes a specified page for quality (spelling, links, etc.); accessibility; and privacy (forms, use of third-party content, etc.).
- WAVE 3.0 is the Web Accessibility Tool from the Temple University Institute on Disabilities. It provides a visual chart of a specified web page, with icons highlighting problem content structures.