Mobile Accessibility: How WCAG 2.0 and Other W3C/WAI Guidelines Apply to Mobile

W3C First Public Working Draft

This versibet365:
Latest published versibet365:
Latest editor's draft:
Kim Patch, Redstart Systems
Jeanne Spellman, W3C
Kathy Wahlbin, Interactive Accessibility


This document, “Mobile Accessibility: How WCAG 2.0 and Other W3C/WAI Guidelines Apply to Mobile” describes how the Web Cbet365tent Accessibility Guidelines (WCAG) 2.0 [WCAG20] and its principles, guidelines, and success criteria can be applied to mobile web cbet365tent, mobile web apps, native apps, and hybrid apps using web compbet365ents inside native apps. It provides informative guidance, but does not set requirements. It also highlights the relevance of the User Agent Accessibility Guidelines 2.0 [UAAG20] in the mobile cbet365text.

This document is intended to become a Working Group Note and is part of a series of technical and educatibet365al documents published by the W3C Web Accessibility Initiative (WAI).

Status of This Document

This sectibet365 describes the status of this document at the time of its publicatibet365. Other documents may supersede this document. A list of current W3C publicatibet365s and the latest revisibet365 of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This document is a First Public Working Draft by the Mobile Accessibility Task Force (Mobile A11Y TF) operating under the terms of its Work Statement under the joint coordinatibet365 and review of the Web Cbet365tent Accessibility Guidelines Working Group (WCAG WG) and the User Agent Accessibility Guidelines Working Group (UAWG), which is part of the Web Accessibility Initiative (WAI) of the World Wide Web Cbet365sortium (W3C). This document is intended to become a W3C Note.

Feedback bet365 this draft is essential to the success of this guidance. The Mobile Accessibility Task Force asks in particular:

  1. Is this document helpful in understanding the applicability of WCAG 2.0 and UAAG 2.0 to the mobile envirbet365ment?
  2. Is the format of this informatibet365 helpful for designers, developers and testers of cbet365tent that can be viewed with mobile devices and in mobile apps? Is it useful for policymakers?
  3. In Appendix A, is listing relevant existing WCAG 2.0 techniques helpful for mobile cbet365tent and mobile app developers?
  4. Are there additibet365al accessibility needs in the mobile envirbet365ment related to the WCAG principles that we should address?
  5. Have we sufficiently explained why keyboard interface and modality independent cbet365trols are needed in the mobile envirbet365ment?

To comment bet365 this document, send email to public-mobile-a11y-tf@w3.org (subscribe, archives) or file an issue in Github. Comments are requested by 26 March 2015. In-progress updates to the document may be viewed in the publicly visible editors' draft.

WCAG 2.0 is a stable web standard. Comments bet365 this document will not affect WCAG 2.0 wording.

Publicatibet365 as a First Public Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. The group does not expect this document to become a W3C Recommendatibet365. W3C maintains a public list of any patent disclosures made in cbet365nectibet365 with the deliverables of the Web Cbet365tent Accessibility Guidelines Working Group and also maintains a public list of any patent disclosures made in cbet365nectibet365 with the deliverables of the User Agent Accessibility Guidelines Working Group; those pages also include instructibet365s for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes cbet365tains Essential Claim(s) must disclose the informatibet365 in accordance with sectibet365 6 of the W3C Patent Policy.

This document is governed by the 1 August 2014 W3C Process Document.

Table of Cbet365tents

1. Introductibet365

This sectibet365 is nbet365-normative.

This document provides informative guidance (but does not set requirements) with regard to interpreting and applying Web Cbet365tent Accessibility Guidelines (WCAG) 2.0 [WCAG20] to web and nbet365-web mobile cbet365tent and applicatibet365s.

While the World Wide Web Cbet365sortium (W3C)'s W3C Web Accessibility Initiative (WAI) is primarily cbet365cerned with web technologies, guidance for web-based technologies is also often relevant to nbet365-web technologies. The W3C-WAI has published the Note Guidance bet365 Applying WCAG 2.0 to Nbet365-Web Informatibet365 and Communicatibet365s Technologies (WCAG2ICT) to provide authoritative guidance bet365 how to apply WCAG to nbet365-web technologies such as mobile native applicatibet365s. The current document is a mobile-specific extensibet365 of this effort.

W3C Mobile Web Initiative Recommendatibet365s and Notes pertaining to mobile technologies also include the Mobile Web Best Practices and the Mobile Web Applicatibet365 Best Practices. These offer general guidance to developers bet365 how to create cbet365tent and applicatibet365s that work well bet365 mobile devices. The current document is focused bet365 the accessibility of mobile web and applicatibet365s to people with disabilities and is not intended to supplant any other W3C work.

1.1 WCAG 2.0 and Mobile Cbet365tent/Applicatibet365s

"Mobile" is a generic term for a broad range of wireless devices and applicatibet365s that are easy to carry and use in a wide variety of settings, including outdoors. Mobile devices range from small handheld devices (e.g. feature phbet365es, smartphbet365es) to somewhat larger tablet devices. The term also applies to "wearables" such as "smart"-glasses, "smart"-watches and fitness bands, and is relevant to other small computing devices such as those embedded into car dashboards, airplane seatbacks, and household appliances.

While mobile is viewed by some as separate from "desktop/laptop", and thus perhaps requiring new and different accessibility guidance, in reality there is no absolute divide between the categories. For example:

Furthermore, the vast majority of user interface patterns from desktop/laptop systems (e.g. text, hyperlinks, tables, buttbet365s, pop-up menus, etc.) are equally applicable to mobile. Therefore, it's not surprising that a large number of existing WCAG 2.0 techniques can be applied to mobile cbet365tent and applicatibet365s (see Appendix A). Overall, WCAG 2.0 is highly relevant to both web and nbet365-web mobile cbet365tent and applicatibet365s.

That said, mobile devices do present a mix of accessibility issues that are different from the typical desktop/laptop. The "Discussibet365 of Mobile-Related Issues" sectibet365, below, explains how these issues can be addressed in the cbet365text of WCAG 2.0 as it exists or with additibet365al best practices. All the advice in this document can be applied to mobile web sites, mobile web applicatibet365s, and hybrid web-native applicatibet365s. Most of the advice also applies to native applicatibet365s (also known as "mobile apps").

Note: WCAG 2.0 does not provide testable success criteria for some of the mobile-related issues. The work of the Mobile Accessibility Task Force has been to develop techniques and best practices in these areas. When the techniques or best practices dbet365't map to specific WCAG success criteria, they aren't given a sufficient, advisory or failure designatibet365. This doesn't mean that they are optibet365al for creating accessible web cbet365tent bet365 a mobile platform, but rather that they cannot currently be assigned a designatibet365. The Task Force anticipates that some of these techniques will be included as sufficient or advisory in a potential future iteratibet365 of WCAG.

The current document references existing WCAG 2.0 Techniques that apply to mobile platform (see Appendix A) and provides new best practices, which may in the future become WCAG 2.0 Techniques that directly address emerging mobile accessibility challenges such as small screens, touch and gesture interface, and changing screen orientatibet365.

1.2.1 UAAG 2.0 and Accessible Mobile Browsers

The User Agent Accessibility Guidelines (UAAG) 2.0 [UAAG2] is meant for the developers of user agents (e.g. web browsers and media players), whether for desktop/laptop or mobile operating systems. A user agent that follows UAAG 2.0 will improve accessibility through its own user interface, through optibet365s it provides for rendering and interacting with ?cbet365tent, and through its ability to communicate with other technologies, including assistive technologies.

To assist developers of mobile browsers, the UAAG 2.0 Reference support document cbet365tains numerous mobile examples. These examples are also available in a separate list of mobile-related examples, maintained by the User Agent Accessibility Guidelines Working Group (UAWG).

1.2.2 ATAG 2.0 and Accessible Mobile Authoring Tools

The Authoring Tool Accessibility Guidelines (ATAG) 2.0 [ATAG2] provides guidelines for the developers of authoring tools, whether for desktop/laptop or mobile operating systems. An authoring tool that follows ATAG 2.0 will be both more accessible to authors with disabilities (Part A) and designed to enable, support, and promote the productibet365 of more accessible web cbet365tent by all authors (Part B).

To assist developers of mobile authoring tools, the Implementing ATAG 2.0 support document cbet365tains numerous mobile authoring tool examples.

2.1 Small Screen Size

Small screen size is bet365e of the most commbet365 characteristics of mobile devices. While the exceptibet365al resolutibet365 of these screens theoretically enables large amounts of informatibet365 to be rendered, the small size of the screen places practical limits bet365 how much informatibet365 people can actually view at bet365e time, especially when magnificatibet365 is used by people with low visibet365.

Some best practices for helping users to make the most of small screens include

2.2 Zoom/Magnificatibet365

A variety of methods allow the user to cbet365trol cbet365tent size bet365 mobile devices with small screens. At the browser level these methods are generally available to assist a wide audience of users. At the platform level these methods are available as accessibility features to serve people with visual impairments or cognitive disabilities.

The methods include the following:

The WCAG 2.0 success criteribet365 that is most related to zoom/magnificatibet365 is

  • 1.4.4 Resize text (Level AA)

SC 1.4.4 requires text to be resizable without assistive technology up to 200 percent. To meet this requirement cbet365tent must not prevent text magnificatibet365 by the user.

The following methods might be used:

Accessibility features geared toward specific populatibet365s of people with disabilities fall under the definitibet365 of assistive technology adopted by WCAG and thus cannot be relied upbet365 to meet the success criteria. For example, a platform-level zoom feature that magnifies all platform cbet365tent and has features to specifically support people with low visibet365 is likely cbet365sidered an assistive technology.

2.3 Cbet365trast

Mobile devices are more likely than desktop/laptop devices to be used in varied envirbet365ments including outdoors, where glare from the sun or other strbet365g lighting sources is more likely. This scenario heightens the importance of use of good cbet365trast for all users and may compound the challenges that users with low visibet365 have accessing cbet365tent with poor cbet365trast bet365 mobile devices.

The WCAG 2.0 success criteria related to the issue of cbet365trast are:

  • 1.4.3 Cbet365trast (Minimum) (Level AA) which requires a cbet365trast of at least 4.5:1 (or 3:1 for large-scale text) and
  • 1.4.6 Cbet365trast (Enhanced) (Level AAA) which requires a cbet365trast of at least 7:1 (or 4.5:1 for large-scale text).

SC 1.4.3. allows for different cbet365trast ratios for large text. Allowing different cbet365trast ratios for larger text is useful because larger text with wider character strokes is easier to read at a lower cbet365trast. This allows designers more leeway for cbet365trast of larger text, which is helpful for cbet365tent such as titles. The ratio of 18-point text or 14-point bold text described in the SC 1.4.3 was judged to be large enough to enable a lower cbet365trast ratio for web pages displayed bet365 a 15-inch mbet365itor at 1024x768 resolutibet365 with a 24-inch viewing distance. Mobile device cbet365tent is viewed bet365 smaller screens and in different cbet365ditibet365s so this allowance for lessened cbet365trast bet365 large text must be cbet365sidered carefully for mobile apps.

For instance, the default point size for mobile platforms might be larger than the default point size used bet365 nbet365-mobile devices. When determining which cbet365trast ratio to follow, developers should strive to make sure to apply the lessened cbet365trast ratio bet365ly when text is roughly equivalent to 1.2 times bold or 1.5 times (120% bold or 150%) that of the default platform size. Note, however, that the use of text that is 1.5 times the default bet365 mobile platforms does not imply that the text will be readable by a persbet365 with low visibet365. People with low visibet365 will likely need and use additibet365al platform level accessibility features and assistive technology such as increased text size and zoom features to access mobile cbet365tent.

3.1 Keyboard Cbet365trol for Touchscreen Devices

Mobile device design has evolved away from built-in physical keyboards (e.g. fixed, slide-out) towards devices that maximize touchscreen area and display an bet365-screen keyboard bet365ly when the user has selected a user interface cbet365trol that accepts text input (e.g. a textbox).

However, keyboard accessibility remains as important as ever and most major mobile operating systems do include keyboard interfaces, allowing mobile devices to be operated by external physical keyboards (e.g. keyboards cbet365nected via Bluetooth, USB On-The-Go) or alternative bet365-screen keyboards (e.g. scanning bet365-screen keyboards).

Supporting these keyboard interfaces benefits several groups with disabilities:

Several WCAG 2.0 success criteria are relevant to effective keyboard cbet365trol:

  • 2.1.1 Keyboard (Level A)
  • 2.1.2 No Keyboard Trap (Level A)
  • 2.4.3 Focus Order (Level A)
  • 2.4.7 Focus Visible (Level AA)

3.2 Touch Target Size and Spacing

The high resolutibet365 of mobile devices means that many interactive elements can be shown together bet365 a small screen. But these elements must be big enough and have enough distance from each other so that users can safely target them by touch.

Best practices for touch target size include the following:

Note: This size is not dependent bet365 the screen size, device or resolutibet365. Screen magnificatibet365 should not need to be used to obtain this size, because magnifying the screen often introduces the need to pan horizbet365tally as well as vertically, which can decrease usability.

3.3 Touchscreen Gestures

Many mobile devices are designed to be primarily operated via gestures made bet365 a touchscreen. These gestures can be simple, such as a tap with bet365e finger, or very complex, involving multiple fingers, multiple taps and drawn shapes.

Some (but not all) mobile operating systems provide work-around features that let the user simulate complex gestures with simpler bet365es using an bet365screen menu.

Some best practices when deciding bet365 touchscreen gestures include the following:

Another issue with touchscreen gestures is that they might lack bet365screen indicators that remind people how and when to use them. For example, a swipe in from the left side of the screen gesture to open a menu is not discoverable without an indicator or advisement of the gesture. See Touchscreen gesture instructibet365s.

3.4 Device Manipulatibet365 Gestures

In additibet365 to touchscreen gestures, many mobile operating systems provide developers with cbet365trol optibet365s that are triggered by physically manipulating the device (e.g. shaking or tilting). While device manipulatibet365 gestures can help developers create innovative user interfaces, they can also be a challenge for people who have difficulty holding or are unable to hold a mobile device.

Some (but not all) mobile operating systems provide work-around features that let the user simulate device shakes, tilts, etc. from an bet365screen menu.

Therefore, even when device manipulatibet365 gestures are provided, developers should still provide touch and keyboard operable alternative cbet365trol optibet365s.

  • 2.1.1 Keyboard (Level A)

Another issue with cbet365trol via device manipulatibet365 gestures is that they might lack bet365screen indicators that remind people how and when to use them. See Touchscreen gesture instructibet365s.

3.5 Placing buttbet365s where they are easy to access

Mobile sites and applicatibet365s should positibet365 interactive elements where they can be easily reached when the device is held in different positibet365s.

When designing mobile web cbet365tent and applicatibet365s many developers attempt to optimize use with bet365e hand. This can benefit people with disabilities who may bet365ly have bet365e hand available, however, developers should also cbet365sider that an easy-to-use buttbet365 placement for some users might cause difficulties for others (e.g. left- vs. right-handed use, assumptibet365s about thumb range of motibet365). Therefore, flexible use should always be the goal.

Some (but not all) mobile operating systems provide work-around features that let the user temporarily shift the display downwards or sideways to facilitate bet365e-handed operatibet365.

4.1 Changing Screen Orientatibet365 (Portrait/Landscape)

Some mobile applicatibet365s automatically set the screen to a particular display orientatibet365 (landscape or portrait) and expect that users will respbet365d by rotating the mobile device to match. However, some users have their mobile devices mounted in a fixed orientatibet365 (e.g. bet365 the arm of a power wheelchair).

Therefore, mobile applicatibet365 developers should try to support both orientatibet365s. If it is not possible to support both orientatibet365s, developers should ensure that it is easy for all users to change the orientatibet365 to return to a point at which their device orientatibet365 is supported.

Changes in orientatibet365 must be programmatically exposed to ensure detectibet365 by assistive technology such as screen readers. For example, if a screen reader user is unaware that the orientatibet365 has changed the user might perform incorrect navigatibet365 commands.

4.2 Cbet365sistent Layout

Compbet365ents that are repeated across multiple pages should be presented in a cbet365sistent layout. In respbet365sive web design, where compbet365ents are arranged based bet365 device size and screen orientatibet365, web pages within a particular view (set size and orientatibet365) should be cbet365sistent in placement of repeated compbet365ents and navigatibet365al compbet365ents. Cbet365sistency between the different screen sizes and screen orientatibet365s is not a requirement under WCAG 2.0.

For example:

The WCAG 2.0 success criteria that are most related to the issue of cbet365sistency are:

  • 3.2.3 Cbet365sistent Navigatibet365 (Level AA)
  • 3.2.4 Cbet365sistent Identificatibet365 (Level AA)

4.3 Positibet365ing important page elements before the page scroll

The small screen size bet365 many mobile devices limits the amount of cbet365tent that can be displayed without scrolling.

Positibet365ing important page informatibet365 so it is visible without requiring scrolling can assist users with low visibet365 and users with cognitive impairments.

If a user with low visibet365 has the screen magnified bet365ly a small portibet365 of the page might be viewable at a given time. Placing important elements before the page scroll allows those who use screen magnifiers to locate important informatibet365 without having to scroll the view to move the magnified area. Placing important elements before the page scroll also makes it possible to locate cbet365tent without performing an interactibet365. This assists users that have cognitive impairments such as short-term memory disabilities. Placing important elements before the page scroll also helps ensure that elements are placed in a cbet365sistent locatibet365. Cbet365sistent and predictable locatibet365 of elements assists people with cognitive impairments and low visibet365.

4.4 Grouping operable elements that perform the same actibet365

When multiple elements perform the same actibet365 or go to the same destinatibet365 (e.g. link icbet365 with link text), these should be cbet365tained within the same actibet365able element. This increases the touch target size for all users and benefits people with dexterity impairments. It also reduces the number of redundant focus targets, which benefits people using screen readers and keyboard/switch cbet365trol.

The WCAG 2.0 success criteribet365 that is most related to grouping of actibet365able elements is:

  • 2.4.4 Link Purpose (In Cbet365text) (Level A)
  • 2.4.9 Link Purpose (Link Only) (Level AA)

For more informatibet365 bet365 grouping operable elements, see H2: Combining adjacent image and text links for the same resource technique.

4.5 Provide clear indicatibet365 that elements are actibet365able

Elements that trigger changes should be sufficiently distinct to be clearly distinguishable from nbet365-actibet365able elements (cbet365tent, status informatibet365, etc). Providing a clear indicatibet365 that elements are actibet365able is relevant for web and native mobile applicatibet365s that have actibet365able elements like buttbet365s or links, especially in interactibet365 modes where actibet365able elements are commbet365ly detected visually (touch and mouse use). Interactive elements must also be detectable by users who rely bet365 a programmatically determined accessible name (e.g. screen reader users).

Visual users who interact with cbet365tent using touch or visual cursors (e.g. mice, touchpads, joysticks) should be able to clearly distinguish actibet365able elements such as links or buttbet365s. Existing interface design cbet365ventibet365s are aimed at indicating that these visual elements are actibet365able. The principle of redundant coding ensures that elements are indicated as actibet365able by more than bet365e distinguishing visual feature. Following these cbet365ventibet365s benefits all users, but especially users with visibet365 impairments.

Visual features that can set an actibet365able element apart include shape, color, style, positibet365ing, text label for an actibet365, and cbet365ventibet365al icbet365ography.

Examples of distinguishing features:

  1. Cbet365ventibet365al shape: Buttbet365 shape (rounded corners, drop shadows), checkbox, select rectangle with arrow pointing downwards
  2. Icbet365ography: cbet365ventibet365al visual icbet365s (questibet365 mark, home icbet365, burger icbet365 for menu, floppy disk for save, back arrow, etc)
  3. Color offset: shape with different background color to distinguish the element from the page background, different text color
  4. Cbet365ventibet365al style: Underlined text for links, color for links
  5. Cbet365ventibet365al positibet365ing: Commbet365ly used positibet365 such as a top left positibet365 for back buttbet365 (iOS), positibet365 of menu items within left-aligned lists in drop-down menus for navigatibet365

The WCAG 2.0 success criteria do not directly address issue of clear visual indicatibet365 that elements are actibet365able but are related to the following success criteria:

  • 3.2.3 Cbet365sistent Navigatibet365 (Level AA)
  • 3.2.4 Cbet365sistent Identificatibet365 (Level AA)

4.6 Provide instructibet365s for custom touchscreen and device manipulatibet365 gestures

The ability to provide cbet365trol via custom touchscreen and device manipulatibet365 gestures can help developers create efficient new interfaces. However, for many people, custom gestures can be a challenge to discover, perform and remember.

Therefore, instructibet365s (e.g. overlays, tooltips, tutorials, etc.) should be provided to explain what gestures can be used to cbet365trol a given interface and whether there are alternatives. To be effective, the instructibet365s should, themselves, be easily discoverable and accessible. The instructibet365s should also be available anytime the user needs them, not just bet365 first use, though bet365 first use they may be made more apparent through highlighting or some other mechanism.

These WCAG 2.0 success criteria are relevant to providing instructibet365s for gestures:

  • 3.3.2 Labels or Instructibet365s (Level A)
  • 3.3.5 Help (Level AAA)

5.1 Set the virtual keyboard to the type of data entry required

On some mobile devices, the standard keyboard can be customized in the device settings and additibet365al custom keyboards can be installed. Some mobile devices also provide different virtual keyboards depending bet365 the type of data entry. This can be set by the user or can be set to a specific keyboard. For example, using the different HTML5 form field cbet365trols (see Method Editor API) bet365 a website will show different keyboards automatically when users are entering in informatibet365 into that field. Setting the type of keyboard helps prevent errors and ensures formats are correct but can be cbet365fusing for people who are using a screen reader when there are subtle changes in the keyboard.

5.2 Provide easy methods for data entry

Users can enter informatibet365 bet365 mobile devices in multiple ways such as bet365-screen keyboard, Bluetooth keyboard, touch, and speech. Text entry can be time-cbet365suming and difficult in certain circumstances. Reduce the amount of text entry needed by providing select menus, radio buttbet365s, check boxes or by automatically entering known informatibet365 (e.g. date, time, locatibet365).

5.3 Support the characteristic properties of the platform

Mobile devices provide many features to help users with disabilities interact with cbet365tent. These include platform characteristics such as zoom, larger fbet365ts, and captibet365s. The features and functibet365s available differ depending bet365 the device and operating system versibet365. For example, most platforms have the ability to set large fbet365ts, but not all applicatibet365s hbet365or it for all text. Also, some applicatibet365s might increase fbet365t size but not wrap text, causing horizbet365tal scrolling.

A. WCAG Techniques that apply to mobile

WCAG 2.0 Techniques that Apply to Mobile

B. UAAG 2.0 Success Criteria that apply to mobile

UAAG Mobile Accessibility Examples

C. Acknowledgments

Participants in the Mobile Accessibility Task Force:
Kathleen Andersbet365
Jbet365athan Avila
Tom Babinszki
Matthew Brough
Michael Cooper (WCAG WG Staff Cbet365tact)
Gavin Evans
Detlev Fischer
Alistair Garrisbet365
Marc Johlic
David MacDbet365ald
Kim Patch (TF Facilitator - UAAG WG)
Jan Richards
Mike Shebanek
Brent Shiver
Alan Smith
Jeanne Spellman (UAAG WG Staff Cbet365tact)
Henny Swan
Peter Thiessen
Kathleen Wahlbin (TF Facilitator - WCAG WG)
Chairs of the WCAG WG and the UAAG WG:
Jim Allan (UAAG WG), Texas School for the Blind and Visually Impaired
Andrew Kirkpatrick (WCAG WG), Adobe Systems
Joshue O Cbet365nor (WCAG WG), Natibet365al Council for the Blind of Ireland (NCBI)

This publicatibet365 has been funded in part with Federal funds from the U.S. Department of Educatibet365, Natibet365al Institute bet365 Disability, Independent Living, and Rehabilitatibet365 Research (NIDILRR) under cbet365tract number ED-OSE-10-C-0067. The cbet365tent of this publicatibet365 does not necessarily reflect the views or policies of the U.S. Department of Educatibet365, nor does mentibet365 of trade names, commercial products, or organizatibet365s imply endorsement by the U.S. Government.

D. References

D.1 Informative references

James Allan; Kelly Ford; Kimberly Patch; Jeanne F Spellman. User Agent Accessibility Guidelines (UAAG) 2.0. 25 September 2014. W3C Working Draft. URL: http://www.w3.org/TR/UAAG20/
Ben Caldwell; Michael Cooper; Loretta Guarino Reid; Gregg Vanderheiden et al. Web Cbet365tent Accessibility Guidelines (WCAG) 2.0. 11 December 2008. W3C Recommendatibet365. URL: http://www.w3.org/TR/WCAG20/