Building with web standards: Web Content Accessibility Guidelines (WCAG)

In 1999, the World Wide Web Consortium (W3C) published a specification on the accessibility of websites, the Web Content Accessibility Guidelines, known by its acronym of WCAG. This specification, in particular the priority 1 and priority 2 levels of the WCAG 1.0, are being implemented worldwide as the norm for building accessible websites.

The checkpoints 12.1 and 12.2 relate to the use of frames. The Web Guidelines do not allow the use of frames. Therefore, in the context of the Web Guidelines neither checkpoint has any further function. In any case, this does not cause compatibility problems.
For completeness sake, however, both checkpoints have been included in the checklist.

http://www.w3.org/TR/WCAG10/full-checklist.html

This table contains all priority 1 and priority 2 requirements of the WCAG 1.0.
Bookmark: The numbers in the first column refer to the World Wide Web Consortium (W3C) checkpoint in question.

no.	General [Priority 1]
1.1	Provide a text equivalent for every non-text element (e.g., via ‘alt’, ‘longdesc’, or in element content). This includes: images, graphical representations of text (including symbols), image map regions, animations (e.g., animated GIFs), applets and programmatic objects, ascii art, frames, scripts, images used as list bullets, spacers, graphical buttons, sounds (played with or without user interaction), stand-alone audio files, audio tracks of video, and video.
2.1	Ensure that all information conveyed with color is also available without color, for example from context or markup.
4.1	Clearly identify changes in the natural language of a document's text and any text equivalents (e.g., captions).
6.1	Organize documents so they may be read without style sheets. For example, when an HTML document is rendered without associated style sheets, it must still be possible to read the document. When content is organized logically, it will be rendered in a meaningful order when style sheets are turned off or not supported.
6.2	Ensure that equivalents for dynamic content are updated when the dynamic content changes.
7.1	Until user agents allow users to control flickering, avoid causing the screen to flicker.
14.1	Use the clearest and simplest language appropriate for a site's content.
no.	When using ‘image maps’ [Priority 1]
1.2	Provide redundant text links for each active region of a server-side image map.
9.1	Provide client-side image maps instead of server-side image maps except where the regions cannot be defined with an available geometric shape.
n0.	When using data tables [Priority 1]
5.1	For data tables, identify row and column headers.
5.2	For data tables that have two or more logical levels of row or column headers, use markup to associate data cells and header cells.
no.	When using frames [Priority 1]
12.1	Title each frame to facilitate frame identification and navigation. For example, in HTML use the "title" attribute on FRAME elements.
no.	When using (Java- en VB-)scripts and/ or applets [Priority 1]
6.3	Ensure that pages are usable when scripts, applets, or other programmatic objects are turned off or not supported. If this is not possible, provide equivalent information on an alternative accessible page.
no.	When using multimedia (audio, video, animation) [Priority 1]
1.3	Until user agents can automatically read aloud the text equivalent of a visual track, provide an auditory description of the important information of the visual track of a multimedia presentation.
1.4	For any time-based multimedia presentation (e.g., a movie or animation), synchronize equivalent alternatives (e.g., captions or auditory descriptions of the visual track) with the presentation.
no.	When it is not possible to make pages accessible [Priority 1]
11.4	If, after best efforts, you cannot create an accessible page, provide a link to an alternative page that uses W3C technologies, is accessible, has equivalent information (or functionality), and is updated as often as the inaccessible (original) page.
no.	General [Priority 2]
2.2	Ensure that foreground and background color combinations provide sufficient contrast when viewed by someone having color deficits or when viewed on a black and white screen [Priority 2 for images, Priority 3 for text].
3.1	When an appropriate markup language exists, use markup rather than images to convey information.
3.2	Create documents that validate to published formal grammars.
3.3	Use style sheets to control layout and presentation.
3.4	Use relative rather than absolute units in markup language attribute values and style sheet property values.
3.5	Use header elements to convey document structure and use them according to specification.
3.6	Mark up lists and list items properly.
3.7	Mark up quotations. Do not use quotation markup for formatting effects such as indentation.
6.5	Ensure that dynamic content is accessible or provide an alternative presentation or page.
7.2	Until user agents allow users to control blinking, avoid causing content to blink (i.e., change presentation at a regular rate, such as turning on and off)
7.4	Until user agents provide the ability to stop the refresh, do not create periodically auto-refreshing pages.
7.5	Until user agents provide the ability to stop auto-redirect, do not use markup to redirect pages automatically. Instead, configure the server to perform redirects.
10.1	Until user agents allow users to turn off spawned windows, do not cause pop-ups or other windows to appear and do not change the current window without informing the user.
11.1	Use W3C technologies when they are available and appropriate for a task and use the latest versions when supported.
11.2	Avoid deprecated features of W3C technologies.
12.3	Divide large blocks of information into more manageable groups where natural and appropriate.
13.1	Clearly identify the target of each link.
13.2	Provide metadata to add semantic information to pages and sites.
13.3	Provide information about the general layout of a site (e.g., a site map or table of contents).
13.4	Use navigation mechanisms in a consistent manner.
no.	If you use tables [Priority 2]
5.3	Do not use tables for layout unless the table makes sense when linearized. Otherwise, if the table does not make sense, provide an alternative equivalent (which may be a linearized version).
5.4	If a table is used for layout, do not use any structural markup for the purpose of visual formatting.
no.	If you use frames [Priority 2]
12.2	Describe the purpose of frames and how frames relate to each other if it is not obvious by frame titles alone.
no.	If you use forms [Priority 2]
10.2	Until user agents support explicit associations between labels and form controls, for all form controls with implicitly associated labels, ensure that the label is properly positioned.
12.4	Associate labels explicitly with their controls.
no.	If you use applets and scripts [Priority 2]
6.4	For scripts and applets, ensure that event handlers are input device-independent.
7.3	Until user agents allow users to freeze moving content, avoid movement in pages.
8.1	Make programmatic elements such as scripts and applets directly accessible or compatible with assistive technologies [Priority 1 if important functionality is not presented elsewhere in the website, otherwise conform to Priority 2.]
9.2	Ensure that any element that has its own interface can be operated in a device-independent manner.
9.3	For scripts, specify logical event handlers rather than device-dependent event handlers.