How Compliance with
Mobile Web Best Practices 1.0
Can Help Users with Disabilities

W3C Working Draft 06 May 2008

Table of Contents


Incomplete draft: This document is an editor's copy that has no official standing and is incomplete. Particularly, the section WCAG 2.0 and MWBP Together is only an outline; WCAG 1.0 to MWBP is only partly filled out. It is subject to major changes and is therefore not intended for implementation. It is provided for review and feedback only. Please send feedback to public-bpwg-comments@w3.org (archive).

This page is part of a suite of related documents. Please refer to the “How to Use These Documents” section for more information.

It describes how different Mobile Web Best Practices (MWBPs) help improve the experience for users with disabilities.

By improving usability, all BPs help improve accessibility. This section describes the specific accessibility benefits and the ways in which some relate directly to the Web Content Accessibility Guidelines 2.0.

Individual Mobile Web Best Practices

This section examines in turn each of the Mobile Web Best Practices where to the Web Content Accessibility Guidelines 2.0. First there is a summary list (“List of Best Practices Described”) for easier navigation. Following it there is a “List of Best Practices not Related to WCAG 2.0”. For each BP, the question considered is: “How does it enhance accessibility to users with disabilities?”.

Users with disabilities benefit from the Mobile Web Best Practices like any other user. This paragraph describes how each BP helps users with disabilities in all contexts of use above and beyond the benefit to the general user in the mobile context. Best Practices that have no specific benefit for users with disabilities beyond that experienced by the general user in the mobile context is marked [no added benefit].

List of Best Practices Described

Below is a list of the BPs described in detail in this section. Each name is a link to the detailed description that follows.

[ACCESS_KEYS] Assign access keys to links in navigational menus and frequently accessed functionality

Some users, for example those with motor disability, are unable to use a mouse even when the context of use allows one. These persons often use only a keyboard or a device that emulates a keyboard. This situation parallels that of all users of mobile devices as these are not usually equipped with a mouse. They also also help people with visual disabilities who can not see the screen well and for those with short-term memory loss or cognitive limitations. Access keys may be helpful for all keyboard users. They are especially (perhaps only) useful when the browser allows the user to discover the keys that are assigned (some do, some don't).

[AUTO_REFRESH] Do not create periodically auto-refreshing pages, unless you have informed the user and provided a means of stopping it

The BP mentions that “Auto-refreshing pages are widely recognized as presenting accessibility problems” but does not explain why. Auto-refresh is especially confusing to users of screen readers. When a page is refreshed a screen reader may begin reading the updated content again from the beginning, causing confusion and preventing the user from ever reading the whole page. It is also a barrier for users of screen magnification, and those with cognitive and reading disabilities. Providing a means to stop auto-refresh may help these users if they are aware of it.

[AVOID_FREE_TEXT] Avoid free text entry where possible.

As described in the explanation of [MINIMIZE_KEYSTROKES] below, this BP is especially beneficial to users with limited dexterity. It is not related to any specific WCAG success criterion.

[BACKGROUND_IMAGE_READABILITY] When using background images make sure that content remains readable on the device

Readability is compromized when there is a lack of contrast with or without a background image. This BP helps users with low vision or color vision deficit (color blindness). Poor readability due to interference by patterns in background images is especially problematic for users with low vision.

[BALANCE] Take into account the trade-off between having too many links on a page and asking the user to follow too many links to reach what they are looking for

Like all users of the small keypads found on mobile devices, users with motor disability may experience special difficulty in using the keyboard or other device to navigate between links. Users with cognitive disability may have difficulty concentrating on large numbers of links. Screen reader users may also have difficulty reading through and remembering a large number of links in order to decide which one they want. Given that human memory can only hold a limited number of items then having to recall more than that many links to choose the right one leads to serious difficulty for blind users. Reducing the number of links helps avoid these difficulties.

[CENTRAL_MEANING] Ensure that material that is central to the meaning of the page precedes material that is not.

Putting the main content first helps keyboard-only users whether in a mobile context or not. It may also help users with cognitive disabilities who have difficulty locating the central information in a page full of navigation links. Users who can only read part of the page at a time, and who tend to start at the beginning, such as those using screen readers or screen magnifiers benefit from this BP.

[CLARITY] Use clear and simple language

It may lead to a writing style that also helps users with innate (rather than contextual) reading difficulties. It will help people who enlarge text or use screen magnification and therefore can not see as much of screen as intended.

[COLOR_CONTRAST] Ensure that foreground and background color combinations provide sufficient contrast

Adequate color and brightness contrast make content more readable for people with low vision.

[CONTROL_LABELLING] Label all form controls appropriately and explicitly associate labels with form controls

For screen reader users who are unable to visually determine the relationship between controls and their labels, it enables assistive technology to determine from markup which label identifies each form control.

[CONTROL_POSITION] Position labels so they lay out properly in relation to the form controls they refer to

If controls are not explicitly associated with their labels (as described under CONTROL_LABELLING in this document) screen readers and who use modified screens use the position in markup of the control and the label to determine the relationship. However, for recent screen readers this is now unnecessary if there is explicit association.

[DEFAULT_INPUT_MODE] Specify a default text entry mode, language and/or input format, if the device is known to support it

While this BP is primarily motivated by the limitations of the input mechanism of the mobile device (for example, a small numeric keypad), it also helps users who have difficulty using their chosen input device. Refer also to PROVIDE_DEFAULTS in this document.

[ERROR_MESSAGES] Provide informative error messages and a means of navigating away from an error message back to useful information

Many users, but especially those with cognitive disabilities or even those with limited experience may have difficulty understanding default error messages and deciding on the correct action to take. This BP aids understanding and navigations.

[FONTS] Do not rely on support of font related styling

Many users do not see fonts-related styling. For example, blind users, those who turn off stylesheets, or use text mode browsers. If information is conveyed by fonts, these users may have difficulty understanding the meaning of content. Refer also STYLE_SHEETS_SUPPORT in this document.

[MEASURES] Do not use pixel measures and do not use absolute units in markup language attribute values and style sheet property values

In addition to the benefits described in the BP, using relative units of measure helps people with low vision by letting them increase text size in content so that they can read it.

[MINIMIZE_KEYSTROKES] Keep the number of keystrokes to a minimum

While mobile devices have input devices such as numeric keypads that are awkward to use for text input. This BP is especially beneficial to users with limited dexterity who find text input even more difficult. It is not related to any specific WCAG 2.0 success criterion.

[NO_FRAMES] Do not use frames

While correctly designed and labeled frames are not inaccessible, equivalent content without frames is generally easier to use. It is easier to scan the whole content with a screen reader and to navigate with the keyboard.

[NON-TEXT_ALTERNATIVES] Provide a text equivalent for every non-text element

Providing text equivalents for non-text content ensures flexibility. Text can be rendered in a diversity of ways such as speech, braille, print, different text sizes. Designing content to be useful when rendered text-only (as required by the BP) requires the provision of text equivalents for non-text content and so may make content more accessible to users unable to see images or other non-text content for whatever reason. Refer to WCAG 2.0 Specific Benefits of Success Criterion 1.1.1 for further information.

[OBJECTS_OR_SCRIPT] Do not rely on embedded objects or script

Users with some disabilities may not be able or willing to install or use the plugins necessary for embedded objects. Others may be unable or unwilling to use script. Some assistive technology may not support scripting or it may be disabled.

[PAGE_SIZE_USABLE] Divide pages into usable but limited size portions

Smaller pages may help users with cognitive limitations who have difficulty with large amounts of text.

[PAGE_TITLE] Provide a short but descriptive page title

People with visual disabilities will benefit from being able to differentiate content when multiple Web pages are open. For example, screen reader users may not be able to see at a glance the content of a window, and so identify it by the page title. People with cognitive disabilities, limited short-term memory and reading disabilities also benefit from the ability to identify content by its title. A descriptive page title also benefits people with severe mobility impairments whose mode of operation relies on audio when navigating between Web pages. Refer to Long page title, with generic information first and differentiating information last.

[POP_UPS] Do not cause pop-ups or other windows to appear and do not change the current window without informing the user

Opening new windows or changing between open windows when the user is not aware what is happening can be confusing to those who can not see that a new or different window has opened, or can not see the window at all. The user may not understand why the back button does not work correctly (the new window has no history or different history list) and may close the last window of the browser instance and close the application inadvertently.

[PROVIDE_DEFAULTS] Provide pre-selected default values where possible

While this BP is primarily motivated by the limitations of the input mechanism of the mobile device (for example, a small numeric keypad), it also helps users who have difficulty using their chosen input device.

[REDIRECTION] Do not use markup to redirect pages automatically. Instead, configure the server to perform redirects by means of HTTP 3xx codes

Like auto-refresh, using markup for redirection can confuse users, especially:

[SCROLLING] Limit scrolling to one direction, unless secondary scrolling cannot be avoided.

This enhances accessibility for users who have difficulty scrolling for whatever reason (device or physical limitation). Limiting scrolling to one direction (particularly the vertical axis), may help people with cognitive limitations. If scrolling is necessary some may not be aware of this; others may be disoriented by horizontal scroll.

[STRUCTURE] Use features of the markup language to indicate logical document structure

Most visual users are able to scan a whole document at a glance. Many non-visual (for example, blind) users are unable to do this and access content starting at the top. When a document is structured with section headings a screen reader or suitable browser can create a table of contents on the fly. A browser may allow keyboard navigation between headings. Refer to WCAG 1.0 HTML Techniques: Section headings for more information.

[STYLE_SHEETS_SUPPORT] Organize documents so that if necessary they may be read without style sheets

When content is organized logically, it will be rendered in a meaningful order when style sheets are turned off or not supported. This particularly helps disabled users who access pages in alternative modes. For example, blind users who use screen readers to access pages in audio, or users with low vision who use screen magnifiers. Visual font effects defined in CSS can not be relied upon a mobile device and many users may not perceive them, for example blind users who use screen readers and users with low vision who substitute authors' stylesheet with a personal stylesheet. For further information, refer to WCAG 2.0 Specific Benefits of Success Criterion 1.3.1 and the explanation of the [FONTS] best practice in this document.

[STYLE_SHEETS_USE] Use style sheets to control layout and presentation, unless the device is known not to support them

Using CSS allows separation of content and presentation, enabling users to adjust presentation to suit their needs. Users with different disabilities benefit from this as it gives flexibility to user agents to adapt content according to the needs of individual users. For example, people with low vision can use their own stylesheets to change font sizes and background colours to meet their needs.

[TAB_ORDER] Create a logical order through links, form controls and objects

While the mobile user may not have a pointing device available a user with (for example) motor disability may need to use the keyboard for navigation. Refer to “Focus (tab) order does not match logical document content sequence” in the accompanying document “Experiences Shared by People with Disabilities and by People Using Mobile Devices”.

[TABLES_LAYOUT] Do not use tables for layout

Reading order: Using tables can cause incorrect reading order (when the apparent visual sequence is not the same as that in the markup). Avoiding tables for layout avoids the problem. Flexibility: if content is formatted with CSS positioning, users can modify layout to suit their needs; with tables the content is locked in a grid.

[TABLES_NESTED] Do not use nested tables

Nested tables can be problematic for users of screen readers. As the screen reader is unable to differentiate between a data table (which conveys meaning) and a layout table (which should not), a screen reader may announce to the user each new table it encounters, and information such as the number of rows and columns the table contains. If tables are nested this can easily result in an excess of information and cause confusion. This best practice avoids the problem.

[TESTING] Carry out testing on actual devices as well as emulators

This BP is concerned with the characteristics of different devices, not different users, and as such does not specifically improve accessibility for users with disabilities. However, it does also encourage content providers to also test “with specific features disabled, such as using text-only modes and with scripting disabled”. This is a way of checking compliance with WCAG 1.0 checkpoints 1.1, “Provide a text equivalent for every non-text element...” and 6.3, “Ensure that pages are usable when scripts, applets, or other programmatic objects are turned off or not supported”.

Tip: You can improve accessibility when performing testing by involving users with a range of abilities (not only evaluation and development staff). Refer to the WAI resource “Involving Users in Web Accessibility Evaluation” for more information.

[URIS] Keep the URIs of site entry points short

Users with motor disability who type URIs using the keyboard or use voice input, or who have dyslexia, may experience difficulty when entering long strings of text. Long URIs can also confuse screen reader users as the page URI is often the first thing they hear. Keeping the URIs short helps all these users. This BP deals with an aspect not considered in WCAG 1.0.

[USE_OF_COLOR] Ensure that information conveyed with color is also available without color.

This BP benefits people with visual disabilities. Users may not be able to see colors or identify them correctly (color deficit, color blindness) or see the page at all (blind users). Users may have turned off the style sheet or use a browser that does not support CSS, or may need to use a special style sheet. These users may misinterpret or not perceive information expressed by color alone.

[VALID_MARKUP] Create documents that validate to published formal grammars

From WCAG 2.0, 4.1.1 Parsing: Ensuring that Web pages have complete start and end tags and are nested according to specification helps ensure that assistive technologies can parse the content accurately and without crashing. Assistive technologies used by disabled users can provide more accurate presentation of pages that validate to published grammars.