From WCAG 2.0 to MWBP: Making content that meets Web Content Accessibility Guidelines 2.0 also meet Mobile Web Best Practices
W3C Working Group Note 9 July 2009
Introduction
This page is part of a multi-page document. Please refer to the “How to Use This Document” section for more information.
For those familiar with Web Content Accessibility Guidelines 2.0, this page describes what also needs to be done to meet Mobile Web Best Practices (MWBP).
Summary of work required to make content that meets WCAG 2.0 also meet MWBP
Compliance with WCAG 2.0 helps go some way towards achieving compliance with some of the MWBP. This section provides a summary of these BPs. There are two possible levels of effort required, labelled for simplicity with the keywords nothing, something and everything. Note that coverage may depend on WCAG compliance level achieved and so a BP may appear in “something” and “nothing” lists (for example, LINK_TARGET_ID). To summarise, if your content already complies with WCAG 2.0, to achieve compliance with the MWBP, you need to do the following:
Nothing: If a provision is labelled “Nothing” then content that complies with WCAG 2.0 already complies with the provision and no further effort is necessary. The following list includes all of the provisions that are marked “Nothing”. Links in this section point to the relevant provisions.
Something: If a provision is labelled “Something” then more effort of some kind is necessary to comply with the provision. All of the provisions marked “Something” are included in the list below. Each item in the list is a link to an explanation of what is required, in the next section of this report. For each there is a list of the provisions that may provide some compliance or are in some way related. There is no direct correspondence between one provision and another. In some cases, it may be necessary to make an extra effort or to consider a more diverse range of user needs. In these cases, the word “possibly” is used. In other cases scope may be different, giving partial compliance. In these cases the word “partially” is used. BP links in this section point to the detail section below; SC links in this section point to WCAG 2.0.
- BACKGROUND_IMAGE_READABILITY, possibly covered at level AA by 1.4.3 Contrast (Minimum) and at level AAA 1.4.6 Contrast (Enhanced)
- COLOR_CONTRAST, partially covered at level AA by success criterion 1.4.3 Contrast (Minimum) and at level AAA 1.4.6 Contrast (Enhanced)
- CONTROL_LABELLING, possibly covered at level A by 1.3.1 Info and Relationships, 3.3.2 Labels or Instructions and 4.1.2 Name, Role, Value.
- CONTROL_POSITION, possibly covered at level A by 1.3.1 Info and Relationships.
- GRAPHICS_FOR_SPACING, possibly covered at level A by 1.3.1 Info and Relationships.
- LINK_TARGET_ID, partially covered at level A by 2.4.4 Link Purpose (In Context).
- MEASURES, possibly covered at level AA by 1.4.4 Resize text.
- NAVIGATION, partially covered at level AA by 3.2.3 Consistent Navigation and at level AAA 2.4.10 Section Headings.
- NON-TEXT_ALTERNATIVES, partially covered at level AAA by 1.2.7 Full Text Alternative (but covered already at that level by 1.1.1 Non-text Content).
- PAGE_TITLE, possibly covered at level A by 2.4.2 Page Titled.
- POP_UPS, partially covered at level A by 3.2.1 On Focus and 3.2.2 On Input and possibly at level AAA by 3.2.5 Change on Request.
- REDIRECTION, covered at level A by 2.2.1 Timing Adjustable and at level AAA by 2.2.4 Interruptions and 3.2.5 Change on Request.
- STRUCTURE, possibly covered at level A by success criterion 1.3.1 Info and Relationships and at level AA by 2.4.6 Headings and Labels and at level AAA by 2.4.10 Section Headings.
- STYLE_SHEETS_SUPPORT, may be covered at level A by success criterion 1.3.1 Info and Relationships.
- VALID_MARKUP, possibly covered at level A by 4.1.1 Parsing.
Everything: For all other BPs, WCAG 2.0 does not ensure compliance and it will be necessary to do the work involved. These BPs are not related to any WCAG 2.0 success criteria.
- ACCESS_KEYS
- AVOID_FREE_TEXT
- BALANCE
- CACHING
- CAPABILITIES
- CENTRAL_MEANING
- CHARACTER_ENCODING_SUPPORT
- CHARACTER_ENCODING_USE
- CLARITY
- CONTENT_FORMAT_PREFERRED
- CONTENT_FORMAT_SUPPORT
- COOKIES
- DEFAULT_INPUT_MODE
- DEFICIENCIES
- ERROR_MESSAGES
- EXTERNAL_RESOURCES
- IMAGE_MAPS
- IMAGES_RESIZING
- IMAGES_SPECIFY_SIZE
- LARGE_GRAPHICS
- LIMITED
- LINK_TARGET_FORMAT
- MINIMIZE
- MINIMIZE_KEYSTROKES
- NAVBAR
- NO_FRAMES
- OBJECTS_OR_SCRIPT
- PAGE_SIZE_LIMIT
- PAGE_SIZE_USABLE
- PROVIDE_DEFAULTS
- SCROLLING
- STYLE_SHEETS_SIZE
- SUITABLE
- TABLES_ALTERNATIVES
- TABLES_LAYOUT
- TABLES_NESTED
- TABLES_SUPPORT
- TESTING
- THEMATIC_CONSISTENCY
- URIS
Addressing Mobile Web Best Practices
This section lists each of the MWBPs that are related to WCAG 2.0 success criteria, which are listed under “something” above. For each BP, the section title is that of the BP. This is followed by a list of the SCs that can help meet it.
Back to Best Practices list.
[BACKGROUND_IMAGE_READABILITY] When using background images make sure that content remains readable on the device
If overall contrast is sufficient, this goes part of the way to ensuring readability with background images.
Back to Best Practices list.
[COLOR_CONTRAST] Ensure that foreground and background color combinations provide sufficient contrast
Unlike MWBP, WCAG specifies a contrast ratio and algorithm and certain types of content that are excluded from the requirement. The following SCs may ensure compliance with this BP. However, note that WCAG allows for exceptions for cases like large text, incidental text or images of text and logotypes. If content covered by the BP is not excluded, then compliance is ensured.
Back to Best Practices list.
[CONTROL_LABELLING] Label all form controls appropriately and explicitly associate labels with form controls
The following SCs ensure compliance with this BP when using label elements to associate text labels with form controls (1.3.1 below), and either 3.3.2 or 4.1.2.
Back to Best Practices list.
[CONTROL_POSITION] Position labels so they lay out properly in relation to the form controls they refer to
- 1.3.1 Info and Relationships at level A, if the label element is used. The advisory (optional) technique (“Positioning labels to maximize predictability of relationships”) is also required to ensure compliance with this BP.
Back to Best Practices list.
- 1.3.1 Info and Relationships at level A, possibly. The SC does not prohibit the use of graphics for spacing, but some of the sufficient techniques may ensure compliance with this BP by encouraging the use of alternatives.
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[LINK_TARGET_ID] Clearly identify the target of each link
- 2.4.4 Link Purpose (In Context) at level A goes some way to meeting this BP, but the SC provides for indicating the link purpose in the context which is not contemplated by the BP, and in the title attribute or table cell header which are unlikely to be supported adequately by a mobile browser. As a result, content that conforms to this SC may not meet the BP.
- 2.4.9 Link Purpose (Link Only) at level AAA ensures compliance with this BP.
Back to Best Practices list.
[MEASURES] Do not use pixel measures and do not use absolute units in markup language attribute values and style sheet property values
WCAG 2.0 does not prohibit the use of the pixel unit of measure.
- 1.4.4 Resize text at level AA helps comply with this BP if named font sizes, em units or percentages are used.
Back to Best Practices list.
[NAVIGATION] Provide consistent navigation mechanisms
Back to Best Practices list.
[NON-TEXT_ALTERNATIVES] Provide a text equivalent for every non-text element
Back to Best Practices list.
[PAGE_TITLE] Provide a short but descriptive page title
- 2.4.2 Page Titled at level A possibly ensures compliance with this BP. However, to comply with the BP, it may be necessary to truncate the title to meet the BP. In this case it may be useful to put the most important, differentiating information first, also helping screen reader users.
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[POP_UPS] Do not cause pop-ups or other windows to appear and do not change the current window without informing the user
- 3.2.1 On Focus at level A may possibly go some way to achieving compliance with this BP, but the SC allows popups.
- 3.2.2 On Input at level A may possibly go some way to achieving compliance with this BP, but the SC allows popups.
- 3.2.5 Change on Request at level AAA may possibly go some way toward compliance, but the SC does allow use of the
target attribute.
Back to Best Practices list.
[REDIRECTION] Do not use markup to redirect pages automatically. Instead, configure the server to perform redirects by means of HTTP 3xx codes
The following SCs go some way to achieving compliance with this BP. Specifically, failure F41: Failure of Success Criterion 2.2.1, 2.2.4, and 3.2.5 due to using meta refresh with a time-out ensures compliance with this BP.
Back to Best Practices list.
[STRUCTURE] Use features of the markup language to indicate logical document structure
The BP is less explicit about what structural elements to use, but the following SCs probably cover its intent.
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[STYLE_SHEETS_SUPPORT] Organize documents so that if necessary they may be read without style sheets
- 1.3.1 Info and Relationships at level A may ensure compliance, if style sheets are not relied on. However, with WCAG 2.0, you can rely on style sheets if you consider it to be an accessibility supported Web technology. It is possible to have all of the information and structure be programmatically determined but the page would not be usable without the style sheets. ARIA is one technology that depends heavily on style sheets and ARIA sites will not be usable (by sighted users) with the style sheets disabled. Also, WCAG 2.0 allows, but does not encourage, layout tables as long as they meet all of the other criteria. The MWBP requires the use of style sheets for layout, and does not allow layout tables, so if layout tables are used, then this SC would not meet the BP.
Back to Best Practices list.
[VALID_MARKUP] Create documents that validate to published formal grammars
- 4.1.1 Parsing may go some way to complying with this BP with some of the sufficient techniques.
Back to Best Practices list.
Updated 27 June 2009.