- From: Kynn Bartlett <kynn@idyllmtn.com>
- Date: Tue, 02 Jun 1998 21:02:05 -0700
- To: w3c-wai-eo@w3.org
Six Principles of Accessible Web Design: An Introduction to the WAI Page Author Guidelines By Kynn Bartlett <kynn@hwg.org> Revision 98/05/02 INTRODUCTION The World Wide Web Consortium's Web Accessibility Project (WAI) has produced an extensive list of guidelines for web page authors with a lot of useful information on designing accessible web pages. Each topic of web authoring, from style and structure to tables to forms, is addressed with detailed instructions on how to maintain accessibility. This very technical document can sometimes be overwhelming to a new web author, however, and the beginner may not gleam the message of the guidelines. Thus, this introduction document is presented as an examination of the _principles_ upon which the Page Author Guidelines were written; the basic rules for accessible design that formed the specific instances described in each individual entry in the guidelines. References after each principle refer back to the guidelines; you should read each entry for complete information. Without further ado: SIX PRINCIPLES OF ACCESSIBLE WEB DESIGN I. Create pages that conform to accepted standards. II. Know the difference between structural and presentational elements; use stylesheets when appropriate. III. Use HTML 4.0 features to provide information about the purpose and function of elements. IV. Make sure your pages can be navigated by keyboard. V. Provide alternative methods to access non-textual content, including images, scripts, multimedia, tables, forms and frames, for user agents that do not display them. VI. Be wary of common pitfalls that can reduce the accessibility of your site. PRINCIPLE I: Create pages that conform to accepted standards. Web pages that follow one of the published standards for HTML, CSS, and other specifications are much more likely to be interpreted correctly by the various user agents (browsers) that exist. If your page is written in "correct" HTML, then you can feel confident you've done your part in providing the user agent with the information it needs to correctly render the page for your browser. Which standard should you use? HTML 4.0 is preferred, since it incorporates a great number of accessibility features and is the latest recognized standard for HTML; however, any of the following should be acceptable: * HTML 4.0 Strict * HTML 4.0 Transitional * HTML 4.0 Frameset * HTML 3.2 * HTML 2.0 Additionally, if you use stylesheets, you should conform to either CSS1 or CSS2, preferably the latter. Relevant Page Author Guidelines: 1-1. [Required] All elements comply with an HTML 4.0 definition and CSS-1. PRINCIPLE II: Know the difference between structural and presentational elements; use stylesheets when appropriate. HTML provides some elements that are strictly "structural" -- meaning that they are used to define the structure for a web page, in semantic terms. "This part is <EM>phasized", "this part is an <ADDRESS>", "this is a <LI>ist item". Other elements represent specific "presentation", such as "this should be in <B>old", or "this is <CENTER>ed in the middle of the line." The HTML 4.0 standard discourages the use of HTML elements to convey presentation; this function is instead given over to stylesheets. It should be noted, though, that stylesheet support is not fully implemented on all user agents; this means that for at least the near future, some presentation elements in HTML will still be used. Relevant Page Author Guidelines: 1-2. [Required] Pages are readable and usable without style sheets (e.g., when the browser does not support them or the user has turned them off). 1-3. [Required] Headings are nested properly and are not used for formatting. 1-4. [Required] List structure and list items are correctly encoded with proper HTML elements. 1-5. [Required] Scrolling or blinking text are not used. 1-6. [Recommended] Text is formatted through style sheets, not by representing it with a graphic (which cannot be searched). 1-7. [Recommended] Invisible or transparent images are not used to force layout. Style sheets are used to control layout. 1-8. [Recommended] Deprecated presentation elements and attributes as well as B and I are not used. 1-9. [Recommended] HTML structural elements are only used to convey meaning, not presentation. 1-10. [Recommended] HTML presentation elements are only used to convey presentation, not structure. 1-11. [Recommended] Horizontal rules, acronyms, and abbreviations have titles. 5-2. [Required] Tables are not used to arrange text documents in columns. PRINCIPLE III: Use HTML 4.0 features to provide information about the purpose and function of elements. HTML 4.0 (and to a limited degree, some previous standards) gives web page authors valuable tools for giving additional information on the function and meaning of various tags, usually through the use of additional attributes such as TITLE or CLASS. These attributes can be interpreted by sufficiently sophisticated user agents to intelligently render the page elements in a way that provides the user with more information -- thus making the web pages more usable for everyone. As an example that graphical browser users may relate to, many web browsers will render the TITLE attribute of images and other elements as "tool tips", small yellow windows that appear when a mouse pointer is passed over the element in question. By providing complete information on what a tag "really means" in the larger scope of your page, you can increase the accessibility of your page. Tables and forms, in particular, can benefit from the new attributes in HTML 4.0. Relevant Page Author Guidelines: 1-12. [Recommended] Provide titles for horizontal rules, acronyms, and abbreviations. 2-4. [Recommended] Images used as links have descriptive link titles. 4-6. [Recommended] Links to very short sounds have titles. 5-1. [Required] Table cells are explicitly associated with row and column labels. 5-4. [Recommended] Tables of text and numbers are available in a linear fashion on an alternative page. 5-5. [Recommended] Lengthy row and column labels are abbreviated. 5-6. [Recommended] Table summaries are available. 5-7. [Recommended] For more complex tables, information is grouped into categories. 7-3. [Required] All frames have titles. 7-4. [Recommended] Links to descriptions of the purpose and layout of frames are provided. 8-2. [Required] Each label is associated with its form control. 8-4. [Recommended] A logical tab order is specified (with the "tabindex" attribute). 8-5. [Recommended] Related controls are grouped (with the FIELDSET element). 8-6. [Recommended] Groups of controls are labeled (with the LEGEND element). 8-7. [Recommended] Menu options are grouped (with the OPTGROUP element). PRINCIPLE IV: Make sure your pages can be navigated by keyboard. Not all users can use, or will have access to, a graphical pointing device such as a mouse. A good web page will be navigatable via keyboard (or voice) commands. While this is often a user agent (browser) issue, there are things that a web author can do that will cause a page to become unusable with keyboard-only. One example is imagemaps -- client-side imagemaps should be used instead of server-side imagemaps, and proper ALT tags provided, because these can be utilized by a browser agent to provide keyboard navigation to the user. Relevent Page Author Guidelines: 2-1. [Required] All images and image maps have alternative text. 2-3. [Required] All image maps are accessible and keyboard navigable. Furthermore: For each client-side image map, each of the map's links has an associated description. For each server-side image map, a list of the map's links are provided as text links (on the same page, on an alternative page that is accessible, or within the body of the OBJECT element). 3-6. [Recommended] Scripts and applets are keyboard operable. 6-3. [Recommended] Links have keyboard shortcuts. 8-10. [Recommended] Form elements have keyboard shortcuts (with the "accesskey" attribute). PRINCIPLE V: Provide alternative methods to access non-textual content, including images, scripts, multimedia, tables, forms and frames, for user agents that do not display them. Not all user agents will be able to display all HTML elements; a wise designer will realize this and plan alternate methods of conveying the same information for user agents which may not be able to fully render the page. The foremost example of this is the "ALT" attribute, of the <IMG> tag, which allows an author to provide alternative text in case an user agent cannot (or does not) display graphics. Likewise, when adding complex elements to your web pages, such as sound, animation, forms, frames, tables, or scripts, you should take advantage of the HTML features that let you specify alternate methods of conveying the same information. The <OBJECT> element is a good example of this; nested <OBJECT>s allow you to specify multiple ways to express the same concept, from a multimedia display down to a plain text summary. Accessibility on some forms can also be maintained by providing "off-line", or at least, off-web methods of doing things; such as providing an email link or phone number for people who can't use a web response form. Relevant Page Author Guidelines: 2-1. [Required] All images and image maps have alternative text. 2-2. [Required] Graphics that present important information (especially charts, tables, and diagrams) have an associated longer description of the graphic (i.e., via a description link or the "longdesc" attribute) Furthermore, authors have included internal text in images for formats that support it. 2-3. [Required] All image maps are accessible and keyboard navigable. Furthermore: For each client-side image map, each of the map's links has an associated description. For each server-side image map, a list of the map's links are provided as text links (on the same page, on an alternative page that is accessible, or within the body of the OBJECT element). 3-1. [Required] Alternative presentations of content are provided for applets and scripts that convey information. 3-2. [Required] Alternative mechanisms are provided for applets and scripts that perform an important function (other than the presentation of information). 3-3. [Required] Applets that require user interaction that cannot be duplicated in an alternative format are directly accessible. 3-5. [Recommended] Applets have alternative text ("alt" on APPLET, "title" on OBJECT). 4-1. [Required] All audio information has an associated transcript. 4-2. [Required] All video information has an associated audio description. 4-3. [Required] All video information has an associated transcript. 4-4. [Required] Transcripts and audio descriptions are synchronized with audio/video information, either directly or via a synchronization file. 4-5. [Recommended] Sounds that play automatically have a visual notification that the sound is playing. 5-3. [Recommended] Tables are not used merely for the purposes of page layout (use style sheets instead). 5-9. [Recommended] A phone number, fax number, or e-mail address is provided if tables can not be made accessible. 7-1. [Required] Each frame document (the FRAMESET element) has a non-frame alternative (e.g., the NOFRAME element). 7-2. [Required] An image does not appear directly in a frame but is part of a document included in a frame. 8-1. [Required] Image maps are not used to create graphical "submit" buttons. 8-3. [Required] Images used as "submit" buttons have alternative text. 8-9. [Recommended] An alternative phone number, fax number, e-mail address, or postal mail address is provided for submitting information. PRINCIPLE VI: Be wary of common pitfalls that can reduce the accessibility of your site. Admittedly, this is a catch-all principle; there are some things that don't fall neatly under the other basic principles, but are important to consider anyway, as they can have a drastic effect on how usable your web site is. Relevant Page Author Guidelines: 2-5. [Recommended] ASCII art has been replaced by images with alternative text. 3-4. [Required] The user can freeze any moving or blinking text. 5-8. [Recommended] Alt-text does not wrap in tables used to position graphics. 6-1. [Recommended] Link text makes sense when read out of context, but is not too verbose. 6-2. [Recommended] Lists of links have non-link, printable characters (surrounded by spaces) between them. 8-8. [Recommended] Edit boxes and text areas have default, place-holding characters. -- Kynn Bartlett <kynn@idyllmtn.com> http://www.idyllmtn.com/~kynn/ Owner, Idyll Mountain Internet http://www.idyllmtn.com/ Board member, HTML Writers Guild http://www.hwg.org/ Virtual Dog Show Co-Coordinator http://www.dogshow.com/ W3C's Web Accessibility Initiative http://www.w3.org/WAI/
Received on Tuesday, 2 June 1998 23:54:48 UTC