Introduction
The Worldwide Web Consortium is in the process of updating its Web Accessibility Guidelines (WCAGs) from 1.0 to 2.0. Web developers should not panic due to the update. If they already have made their websites and web applications in accordance with WCAG 1.0, their products probably will conform to WCAG 2.0 also.

Nevertheless, WCAG 2.0 presents changes that simplify the process of making a product accessible. Unlike WCAG 1.0, WCAG 2.0 is not based on specific HTML or CSS techniques only to implement each recommendation. Therefore, WCAG 2.0 can be applied not only to websites but also to Flash or Powerpoint presentations, PDF, and other applications.

The updated WCAGs are based on four principles that are termed perceivable, operable, understandable, and robust. Under each principle, straightforward guidelines and success criteria are provided that are not ambiguous. In fact, they have “understanding” links that offers clear explanations, examples, and failures of implementations (i.e. not updating ALT attributes when graphics are changed. The guidelines also have “how to meet” links that describe different techniques for remediation according to the application type.

Another difference between WCAG 1.0 and WCAG 2.0 is their ratings. Unlike the former guidelines that are based on priorities, the latter are based on levels. Accordingly, each WCAG 2.0 guideline is equally important to implement. For instance, adding text equivalents for users with visual impairments is just as important as making interface keyboard accessible for users with mobility impairments.

Having the updated guidelines categorized by level, however, is a gauge for conformance. Since applying text alternatives to non-text content (WCAG 2.0, 1.1.1) is Level A, then the item has minimum conformance. On the other hand, since applying text alternatives for live audio-only is Level AAA, then the item has maximum conformance. In short, Level A conformance relates to general, Level AA to more specific, and Level AAA to most specific issues.

Perceivable
The principle pertains to users with hearing or vision impairments. Like WCAG 1.0., the Perceivable Principle of WCAG 2.0 has success criteria to provide text equivalents for images, audio, multimedia presentations, and color-conveyed information. Unlike Guideline 1 of WCAG 1.0, the Perceivable Principle includes recommendations for captcha, images used for security purposes that are hard to decipher. The Perceivable Principle also specifies that decorative graphics should be ignored by assistive technologies (AT). Another notable change is that it recommends sign language interpretation as an accompaniment for synchronized media.

Besides text equivalents, a guideline for structural markup falls under the Perceivable Principle. The 1.3 Adaptable Guideline includes table markup, heading markup, form field labeling and grouping, and list grouping. Although these items are covered in several guidelines under WCAG 1.0, the recommendations remain the same.

Operable
Keyboard accessibility falls under the Operable Principle. Checkpoints 6.4, 9.2, and 9.3 of WCAG 1.0 refer to it as device-independence, which means that an interface can be accessed with the mouse and through the keyboard. The 2.1 Guideline of WCAG 2.0 specifically states “make all functionality available from a keyboard.” Unlike WCAG 1.0, the keyboard guideline of WCAG 2.0 says MouseKeys are not substitutes for keyboard accessibility and that interfaces must obtain keyboard focus.

The Operable principle also includes requirements about timed responses, which WCAG 1.0 does not have. WCAG 2.0’s 2.2 Enough Time Guideline has criteria about time adjustments and no time limits. Additionally, the guideline has a requirement regarding information being lost because of time limits.

As checkpoint 7.1 and 7.2 of WCAG 1.0 mention blinking and flashing, so does the 2.3 Seizures Guideline of WCAG 2.0. However, the latter explicitly suggests that flashes cannot be more than three per second, whereas the 7.1 checkpoint only mentions that seizures can be triggered by flashing with between four and fifty-nine instances per second.
Understandable
The Understanding principle not only can involve users with cognitive disabilities but all other users also. Unlike WCAG 1.0 that dedicated only three checkpoints under Guideline 14, WCAG 2.0 offers several other requirements that pertain to comprehension. For instance, WCAG 2.0’s 3.1 Readable Guideline includes criteria on unusual words, page languages, pronunciation, and abbreviations.
Robust
As mentioned in the Introduction, WCAG 2.0 does not only apply to standard HTML technologies but also other technologies, such as Flash and PowerPoint. In other words, contrary to WCAG 1.0, WCAG 2.0 specifically mentions the Microsoft Active Accessibility (MSAA) information (i.e., Name, State, Role) under 4.1 Compatible Guideline.

No Longer Required
Because web technologies have changed, some checkpoints in WCAG 1.0 are no longer required and, therefore, are excluded from WCAG 2.0. For example, redundant text links for client-side image maps are unnecessary because text alternatives can be provided for map areas. Implicitly associated labels for form elements and place-holding text in edit boxes also are not required since browsers support explicit labeling now. Additionally, list tags have made printable characters between links obsolete.

Other examples of outdated or unnecessary requirements are as follows:
• Summaries and abbreviations for headers in
data tables

• Word-wrapped linearization of layout tables

• Depreciated features of W3C technologies

• Information so that users may receive ]
documents according to their preferences

• Description of the purpose of frames and how
frames relate to each other if it is not
obvious by frame titles alone

• Metadata

• Navigation bars

• Different search levels for a website

• A skip-over method for ASCII art

References
“Web Content Accessibility Guidelines”
http://www.w3.org/TR/WCAG20/

“Comparison of WCAG 1.0 Checkpoints to WCAG 2.0, in Numerical Order”
http://www.w3.org/WAI/WCAG20/from10/comparison/

“Differences Between WCAG 1.0 and WCAG 2.0”