Aria (A)
ARIA, shorthand for “Accessible Rich Internet Applications”, is a set of attributes you can add to HTML elements that define ways to make content and applications accessible to users who use assistive technologies (e.g. screen readers, magnifiers etc.). When accessibility issues cannot be managed with native HTML, ARIA can help bridge those gaps – it can be used to provide information about roles, states, and properties of elements that may not be available through HTML alone.
The a11y issues covered here relate to WCAG Level A rules for ARIA attributes.