Why it matters
Invalid values (e.g. aria-expanded="yes", aria-controls pointing at nothing) are ignored or misannounced.
How to fix it
Use a value the attribute allows (true or false, a token, a number), and make id references point at elements that exist.
References
More accessibility rules
void a11y reports 48 rules in this category. WCAG 2.2 AA through axe-core, plus checks axe can't do alone: visible keyboard focus, 24/44px target size on mobile, 320px reflow and disabled zoom.
aria-required-childrenARIA role is missing required childrenaria-required-parentARIA role is missing its required parentaria-rolesInvalid ARIA rolearia-valid-attrInvalid ARIA attribute namearia-hidden-focusFocusable element inside aria-hiddenaria-hidden-bodyaria-hidden on <body>aria-command-nameARIA button/link/menuitem has no accessible namearia-input-field-nameARIA input field has no accessible name