Impact on users

The following is an overview of common coding accessibility errors and the impact on users with a disability.

Non-text content which has no text-equivalent

When text alternatives are not provided for non-text content, information cannot be rendered by assistive technologies into other forms that people may need, such as large print, braille, speech, simpler language or custom colour combinations.

Similarly, users who find it hard to understand visual information (such as drawings, photos, or graphs) will not be able to access the content. Providing a text presentation of video content on the page will allow people who have a hearing impairment or who are deaf to read the information.

Information and structure which can’t be programmatically determined

When elements are used in a way that does not match their semantic meaning, information, structure and relationship of content may be lost when the presentation format changes. Assistive technologies and user agents may not be able to correctly interpret information and correctly adapt the presentation to a visual, auditory, or tactile format.

Text which cannot be resized

When text cannot be resized up to 200 percent by the user, some people with a vision impairment will be unable to read the information. Text should not lose content or functionality when resized, and users should not need a screen reader (or other assistive technology) to do this – a browser should be sufficient.

Web pages that are not keyboard accessible

Content, controls and interactive elements that cannot be accessed and/or operated via the keyboard will not be available to keyboard users.

When a keyboard user encounters a keyboard trap and is unable to exit a site feature or content area they are effectively stuck and must close the browser window and start again.

Without a visible keyboard focus indicator on all items such as links, navigations, form fields and controls, the keyboard user is unable to see where they are on the page and take their desired action.

When the presentation of an item does not change on keyboard focus, a keyboard user may be unable to navigate around the site, locate desired information and activate functionality.

Text is moving, blinking or scrolling

Moving, blinking, flashing or scrolling text can be a severe distraction or barrier to users who have difficulty reading. This impacts people with low literacy, reading and intellectual disabilities. Also, users with attention deficit disorders can find it hard to focus on sections of the page.

Content should not trigger seizures

When general and red flash thresholds are violated, a seizure may be triggered in people with photosensitive epilepsy and other photosensitive seizure disorders.

Mechanisms are not provided to help people find information

When the keyboard focus order of a web page is altered, the focus may no longer be consistent with the visual reading order. Users with mobility impairments, reading difficulties, visual impairments, and screen magnification users may find the tabbing focus sequence confusing, or be unable to find the focus at all.

People rely on mechanisms to find information that are most suited to their needs. On a large website, if a search is not provided, blind users may find it cumbersome to tab through a large navigation block, or visually impaired users may find it difficult and confusing when doing the same with a screen magnifier or screen reader. Providing a search benefits everyone by allowing information to found quicker.

Text that is not readable and understandable

When the page language is not identified text may not be rendered accurately by user agents and assistive technologies. Users may also experience pronunciation rules not being loaded by text-to-speech software, language characters and scripts not being displayed correctly by browsers, and captions not being shown correctly.

Web pages that are not compatible with technologies

When the DOCTYPE is not specified, information about what version of HTML the page is written in will not be passed on to the web browser, and the content may not be rendered correctly by various user agents and assistive technologies.