Web Accessibility Testing Principles – Part 3

In the first part of the blog series on `Web Accessibility Testing‘, I gave an overview of the importance of accessibility testing and its pertinence for differently enabled people. In the second part, I briefly discussed the process of implementing the same. In this part, I will delve into the principles of Accessible Design.

Given below is a list of some key principles of accessible design. Most accessibility principles can be implemented very easily and will not impact the overall “look and feel” of your web site.

Web accessibility testing principles

Principle 1: Perceivable – Information and user interface components must be presentable to users in ways they can perceive.

1.1. Provide appropriate alternative text

All non-text content that is presented to the user has a text alternative that serves the equivalent purpose, except for the situations listed below.If non-text content is a control or accepts user input, then it has a name that describes its purpose.

1.2. Provide alternatives for time-based media.

An alternative for time-based media is provided that presents equivalent information for prerecorded audio-only content. Either an alternative for time-based media or an audio track is provided that presents equivalent information for prerecorded video-only content.

1.3. Create content that can be presented in different ways without losing information or structure.

Information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text. When the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined.

1.4. Make it easier for users to see and hear content including separating foreground from background.

Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.If any audio on a Web page plays automatically for more than 3 seconds, either a mechanism is available to pause or stop the audio, or a mechanism is available to control audio volume independently from the overall system volume level.

Principle 2: Operable – User interface components and navigation must be operable.

2.1 Keyboard Accessible: Make all functionality available from a keyboard.

All functionality of the content is operable through a keyboard interface without requiring specific timings for individual keystrokes, except where the underlying function requires input that depends on the path of the user’s movement and not just the endpoints.

2.2 Provide users enough time to read and use content.

The time limit is essential and extending it would invalidate the activity.The user is warned before time expires and given at least 20 seconds to extend the time limit with a simple action, and the user is allowed to extend the time limit at least ten times.

2.3 Seizures: Do not design content in a way that is known to cause seizures.

Web pages do not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds.Web pages do not contain anything that flashes more than three times in any one second period.

2.4 Provide ways to help users navigate, find content, and determine where they are.

A mechanism is available to bypass blocks of content that are repeated on multiple Web pages.Web pages have titles that describe topic or purpose.If a Web page can be navigated sequentially and the navigation sequences affect meaning or operation, focusable components receive focus in an order that preserves meaning and operability.

Principle 3: Understandable – Information and the operation of user interface must be understandable.

3.1 Readable: Make text content readable and understandable.

The human language of each passage or phrase in the content can be programmatically determined except for proper names, technical terms, words of indeterminate language, and words or phrases that have become part of the vernacular of the immediately surrounding text.A mechanism is available for identifying specific definitions of words or phrases used in an unusual or restricted way, including idioms and jargon.

3.2 Predictable: Make Web pages appear and operate in predictable ways.

When any component receives focus, it does not initiate a change of context.Changing the setting of any user interface component does not automatically cause a change of context unless the user has been advised of the behavior before using the component.

3.3 Help users avoid and correct mistakes.

If an input error is automatically detected, the item that is in error is identified and the error is described to the user in text.Labels or instructions are provided when content requires user input.If an input error is automatically detected and suggestions for correction are known, then the suggestions are provided to the user, unless it would jeopardize the security or purpose of the content.

Principle 4: Robust – Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies. 

4.1 Maximize compatibility with current and future user agents, including assistive technologies.

In content implemented using markup languages, elements have complete start and end tags, elements are nested according to their specifications, elements do not contain duplicate attributes, and any IDs are unique, except where the specifications allow these features.For all user interface components (including but not limited to: form elements, links and components generated by scripts), the name and role can be programmatically determined; states, properties, and values that can be set by the user can be programmatically set; and notification of changes to these items is available to user agents, including assistive technologies.


The web offers so many opportunities to people with disabilities that are unavailable through any other medium. It offers independence and freedom. However, if a web site is not created with web accessibility in mind, it may exclude a segment of the population that stands to gain the most from the internet. Most people do not intend to exclude people with disabilities. As organizations and designers we should be aware of and implement accessibility, this would ensure that their content can be accessed by a broader population.


  • Ashwini Kanade

    Ashwini works with Trigent Software as Senior Test Engineer. She has nearly seven year of experience in QA for various Web and desktop applications. Ashwini has strong expertise in manual testing, SQL testing and accessibility testing. She has worked on several domains such as CRM, ERP, Education, Localization, Mortgage and Health Sciences.