accessibility-auditor（无障碍审核员）

Accessibility Auditor

Comprehensive guidance for creating accessible web experiences that comply with WCAG standards and serve users of all abilities effectively.

When to Use This Skill

Use this skill when:

• Auditing websites for accessibility compliance
• Implementing WCAG 2.1 Level AA or AAA standards
• Fixing accessibility violations and errors
• Testing with screen readers (NVDA, JAWS, VoiceOver)
• Ensuring keyboard navigation works correctly
• Implementing ARIA attributes and landmarks
• Preparing for ADA or Section 508 compliance audits
• Designing inclusive user experiences

WCAG 2.1 Principles (POUR)

1. Perceivable

Users must be able to perceive the information being presented.

2. Operable

Users must be able to operate the interface.

3. Understandable

Users must be able to understand the information and interface.

4. Robust

Content must be robust enough to work with current and future technologies.

Common Accessibility Issues & Fixes

1. Missing Alt Text for Images

❌ Problem:

<img src="/products/shoes.jpg">

✅ Solution:

<!-- Informative image -->
<img src="/products/shoes.jpg" alt="Red Nike Air Max running shoes with white swoosh">

<!-- Decorative image -->
<img src="/decorative-pattern.svg" alt="" role="presentation">

<!-- Logo that links -->
<a href="/">
  <img src="/logo.png" alt="Company Name - Home">
</a>

Rules:

• Informative images: Describe the content/function
• Decorative images: Use empty alt (alt="")
• Functional images: Describe the action
• Complex images: Provide detailed description nearby

2. Low Color Contrast

❌ Problem:

/* Contrast ratio 2.5:1 - Fails WCAG */
.text {
  color: #767676;
  background: #ffffff;
}

✅ Solution:

/* Contrast ratio 4.5:1+ - Passes AA */
.text {
  color: #595959;
  background: #ffffff;
}

/* Contrast ratio 7:1+ - Passes AAA */
.text-high-contrast {
  color: #333333;
  background: #ffffff;
}

Requirements:

• Normal text (< 18px): 4.5:1 minimum (AA), 7:1 enhanced (AAA)
• Large text (≥ 18px or ≥ 14px bold): 3:1 minimum (AA), 4.5:1 enhanced (AAA)
• UI components and graphics: 3:1 minimum

3. Non-Semantic HTML

❌ Problem:

<div class="button" onclick="submitForm()">Submit</div>
<div class="heading">Page Title</div>
<div class="nav-menu">...</div>

✅ Solution:

<button type="submit" onclick="submitForm()">Submit</button>
<h1>Page Title</h1>
<nav aria-label="Main navigation">...</nav>

Semantic Elements:

• <button> for buttons
• <a> for links
• <h1> - <h6> for headings (hierarchical)
• <nav>, <main>, <aside>, <article>, <section> for landmarks
• <ul>, <ol>, <li> for lists
• <table>, <th>, <td> for tabular data

4. Missing Form Labels

❌ Problem:

<input type="email" placeholder="Enter your email">

✅ Solution:

<!-- Explicit label -->
<label for="email">Email Address</label>
<input type="email" id="email" name="email">

<!-- Implicit label -->
<label>
  Email Address
  <input type="email" name="email">
</label>

<!-- Hidden label (for tight layouts) -->
<label for="search" class="sr-only">Search</label>
<input type="text" id="search" placeholder="Search...">

Best Practices:

• Every form field must have an associated label
• Labels should be visible (don't rely on placeholder)
• Use aria-label only when visual label isn't possible
• Group related fields with <fieldset> and <legend>

5. Keyboard Navigation Issues

❌ Problem:

<div onclick="handleClick()">Click me</div>
<a href="javascript:void(0)" onclick="doSomething()">Action</a>

✅ Solution:

<!-- Use proper button -->
<button onclick="handleClick()">Click me</button>

<!-- If div required, make it accessible -->
<div
  role="button"
  tabindex="0"
  onclick="handleClick()"
  onkeydown="handleKeyPress(event)"
>
  Click me
</div>

<script>
function handleKeyPress(event) {
  if (event.key === 'Enter' || event.key === ' ') {
    event.preventDefault();
    handleClick();
  }
}
</script>

Keyboard Requirements:

• All interactive elements must be keyboard accessible
• Visible focus indicators (outline or custom styling)
• Logical tab order (matches visual flow)
• Skip links for repetitive content
• No keyboard traps (users can navigate away)

6. Missing ARIA Landmarks

❌ Problem:

<div class="header">...</div>
<div class="main-content">...</div>
<div class="sidebar">...</div>
<div class="footer">...</div>

✅ Solution:

<header role="banner">
  <nav aria-label="Main navigation">...</nav>
</header>

<main role="main">
  <h1>Page Title</h1>
  <article>...</article>
</main>

<aside role="complementary" aria-label="Related articles">
  ...
</aside>

<footer role="contentinfo">
  ...
</footer>

Common Landmarks:

• banner - Site header
• navigation - Navigation menus
• main - Primary content (one per page)
• complementary - Supporting content
• contentinfo - Site footer
• search - Search functionality
• form - Form regions

7. Inaccessible Modals/Dialogs

❌ Problem:

<div class="modal">
  <div class="content">
    Modal content
    <button onclick="closeModal()">Close</button>
  </div>
</div>

✅ Solution:

<div
  role="dialog"
  aria-modal="true"
  aria-labelledby="modal-title"
  aria-describedby="modal-desc"
>
  <h2 id="modal-title">Confirm Action</h2>
  <p id="modal-desc">Are you sure you want to delete this item?</p>

  <button onclick="confirmAction()">Confirm</button>
  <button onclick="closeModal()">Cancel</button>
</div>

<script>
// Focus management
function openModal() {
  const modal = document.querySelector('[role="dialog"]');
  const focusableElements = modal.querySelectorAll(
    'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
  );

  // Store previous focus
  previousFocus = document.activeElement;

  // Focus first element
  focusableElements[0].focus();

  // Trap focus
  modal.addEventListener('keydown', trapFocus);
}

function closeModal() {
  // Return focus
  if (previousFocus) previousFocus.focus();
}

function trapFocus(event) {
  if (event.key !== 'Tab') return;

  const focusableElements = Array.from(
    modal.querySelectorAll('button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])')
  );

  const firstElement = focusableElements[0];
  const lastElement = focusableElements[focusableElements.length - 1];

  if (event.shiftKey && document.activeElement === firstElement) {
    lastElement.focus();
    event.preventDefault();
  } else if (!event.shiftKey && document.activeElement === lastElement) {
    firstElement.focus();
    event.preventDefault();
  }
}
</script>

Modal Requirements:

• role="dialog" or role="alertdialog"
• aria-modal="true" to indicate modal behavior
• aria-labelledby pointing to title
• aria-describedby for description (optional)
• Focus management (trap and restore)
• Close on Escape key
• Prevent background scrolling

8. Missing Skip Links

✅ Solution:

<a href="#main-content" class="skip-link">
  Skip to main content
</a>

<header>
  <nav>...</nav>
</header>

<main id="main-content" tabindex="-1">
  <!-- Page content -->
</main>

<style>
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: #000;
  color: #fff;
  padding: 8px;
  text-decoration: none;
  z-index: 100;
}

.skip-link:focus {
  top: 0;
}
</style>

ARIA Best Practices

ARIA Attributes Reference

States:

• aria-checked - Checkbox/radio state
• aria-disabled - Disabled state
• aria-expanded - Expanded/collapsed state
• aria-hidden - Hidden from assistive technology
• aria-pressed - Toggle button state
• aria-selected - Selected state

Properties:

• aria-label - Accessible name
• aria-labelledby - ID reference for label
• aria-describedby - ID reference for description
• aria-live - Live region updates
• aria-required - Required field
• aria-invalid - Validation state

Live Regions

<!-- Polite: Wait for pause in speech -->
<div aria-live="polite" aria-atomic="true">
  Item added to cart
</div>

<!-- Assertive: Interrupt immediately -->
<div aria-live="assertive" role="alert">
  Error: Payment failed
</div>

<!-- Status message -->
<div role="status" aria-live="polite">
  Saving changes...
</div>

Custom Components

Accordion:

<div class="accordion">
  <button
    aria-expanded="false"
    aria-controls="panel-1"
    id="accordion-1"
  >
    Section 1
  </button>
  <div id="panel-1" role="region" aria-labelledby="accordion-1" hidden>
    Panel content
  </div>
</div>

Tabs:

<div role="tablist" aria-label="Content sections">
  <button
    role="tab"
    aria-selected="true"
    aria-controls="panel-1"
    id="tab-1"
  >
    Tab 1
  </button>
  <button
    role="tab"
    aria-selected="false"
    aria-controls="panel-2"
    id="tab-2"
    tabindex="-1"
  >
    Tab 2
  </button>
</div>

<div role="tabpanel" id="panel-1" aria-labelledby="tab-1">
  Panel 1 content
</div>
<div role="tabpanel" id="panel-2" aria-labelledby="tab-2" hidden>
  Panel 2 content
</div>

Testing Checklist

Automated Testing

• Run axe DevTools or WAVE browser extension
• Check HTML validation (W3C Validator)
• Test color contrast ratios
• Verify heading hierarchy
• Check for missing alt text

Manual Testing

• Navigate entire site using only keyboard (Tab, Enter, Escape, Arrow keys)
• Test with screen reader (NVDA, JAWS, or VoiceOver)
• Verify focus indicators are visible
• Check form validation messages are announced
• Test modal focus trapping
• Verify skip links work
• Test with browser zoom at 200%
• Check page reflow at different viewport sizes
• Disable JavaScript and verify core functionality
• Test with Windows High Contrast mode

Screen Reader Testing

VoiceOver (Mac):

• Enable: Cmd + F5
• Navigate: Control + Option + Arrow keys
• Read all: Control + Option + A

NVDA (Windows):

• Navigate: Arrow keys (browse mode) or Tab (focus mode)
• Read all: NVDA + Down Arrow
• Elements list: NVDA + F7

Test Scenarios:

• Can users understand page structure?
• Are headings descriptive and hierarchical?
• Are form labels clear and associated?
• Are error messages announced?
• Can users complete key tasks without vision?

Accessibility Statement

Include on website:

# Accessibility Statement

We are committed to ensuring digital accessibility for people with disabilities. We continually improve the user experience for everyone and apply relevant accessibility standards.

## Conformance Status
This website is partially conformant with WCAG 2.1 Level AA. "Partially conformant" means that some parts of the content do not fully conform to the accessibility standard.

## Feedback
We welcome your feedback on the accessibility of this site. Please contact us:
- Email: accessibility@example.com
- Phone: +1-555-0123

## Known Issues
- [List any known accessibility issues and planned fixes]

Last updated: [Date]

Resources

Tools:

• axe DevTools (browser extension)
• WAVE (web accessibility evaluation tool)
• Lighthouse (Chrome DevTools)
• Colour Contrast Analyser
• Screen readers: NVDA, JAWS, VoiceOver

Guidelines:

• WCAG 2.1: https://www.w3.org/WAI/WCAG21/quickref/
• ARIA Authoring Practices: https://www.w3.org/WAI/ARIA/apg/

Accessibility is not optional—it's a fundamental requirement for creating inclusive web experiences. Prioritize it from the start of every project, not as an afterthought.