This is going to be a tracker for all issues covering (not just obeying) WCAG 2.0 conformance, sorted by WCAG 2.0 norm.
This tracker should help us achieve the stated goal of WCAG 2.0 and ATAG 2.0 level AA conformity for Drupal core.
Please help adding relevant, preexisting issues to this list, and create only sub-issues that you continue to care of, because too many stale issue stubs would end up being unmanagable!
WCAG 2.0 Guidelines
1 Perceivable
1.1 Text Alternatives
#2034999: [meta] Comply with WCAG 1.1: Text Alternatives
1.2 Time-based Media
1.2.1 (A) Audio-only and Video-only (Prerecorded)
1.2.2 (A) Captions (Prerecorded)
1.2.3 (A) Audio Description or Media Alternative (Prerecorded)
1.2.4 (AA) Captions (Live)
1.2.5 (AA) Audio Description (Prerecorded)
1.2.6 (AAA) Sign Language (Prerecorded)
1.2.7 (AAA) Extended Audio Description (Prerecorded)
1.2.8 (AAA) Media Alternative (Prerecorded)
1.2.9 (AAA) Audio-only (Live)
1.3 Adaptable
1.3.1 (A) Info and Relationships
1.3.2 (A) Meaningful Sequence
1.3.3 (A) Sensory Characteristics
1.4 Distinguishable
1.4.1 (A) Use of Color
1.4.2 (A) Audio Control
1.4.3 (AA) Contrast (Minimum)
1.4.4 (AA) Resize text
1.4.5 (AA) Images of Text
1.4.6 (AAA) Contrast (Enhanced)
1.4.7 (AAA) Low or No Background Audio
1.4.8 (AAA) Visual Presentation
1.4.9 (AAA) Images of Text (No Exception)
2.1 Keyboard Accessible
2.1.1 (A) Keyboard
2.1.2 (A) No Keyboard Trap
2.1.3 (AAA) Keyboard (No Exception)
2.2 Enough Time
2.2.1 (A) Timing Adjustable
2.2.2 (A) Pause, Stop, Hide
2.2.3 (AAA) No Timing
2.2.4 (AAA) Interruptions
2.2.5 (AAA) Re-authenticating
2.3 Seizures
2.3.1 (A) Three Flashes or Below Threshold
2.3.2 (AAA) Three Flashes
2.4 Navigable
2.4.1 (A) Bypass Blocks
2.4.2 (A) Page Titled
2.4.3 (A) Focus Order
2.4.4 (A) Link Purpose (In Context)
2.4.5 (AA) Multiple Ways
2.4.6 (AA) Headings and Labels
2.4.7 (AA) Focus Visible
2.4.8 (AAA) Location
2.4.9 (AAA) Link Purpose (Link Only)
2.4.10 (AAA) Section Headings
3.1 Readable
3.1.1 (A) Language of Page
3.1.2 (AA) Language of Parts
#1165466: Language of parts, accessibility and multilanguage: language button
#1993928: Ability to set the lang attribute on specific elements for WCAG 2.0 compliance
3.1.3 (AAA) Unusual Words
3.1.4 (AAA) Abbreviations
3.1.5 (AAA) Reading Level
3.1.6 (AAA) Pronunciation
3.2 Predictable
3.2.1 (A) On Focus
3.2.2 (A) On Input
3.2.3 (AA) Consistent Navigation
3.2.4 (AA) Consistent Identification
3.2.5 (AAA) Change on Request
3.3 Input Assistance
3.3.1 (A) Error Identification
3.3.2 (A) Labels or Instructions
3.3.3 (AA) Error Suggestion
3.3.4 (AA) Error Prevention (Legal, Financial, Data)
3.3.5 (AAA) Help
3.3.6 (AAA) Error Prevention (All)
4.1 Compatible
#2035139: [meta] Comply with WCAG guideline 4.1: Compatibility
(see latest version of: Understanding WCAG 2.0)