Css Module 29

  Module 29: CSS Accessibility Best Practices – Improving Usability and Compliance with WCAG.

This module explores the importance of accessible CSS design, ensuring usability and compliance with the Web Content Accessibility Guidelines (WCAG). We will cover key CSS techniques that improve accessibility, practical exercises, and lab experiments to reinforce learning.

Learning Objectives

By the end of this module, learners will be able to:

Understand WCAG principles and their impact on CSS.

Apply CSS techniques to improve readability, navigation, and responsiveness.

Conduct accessibility tests and audits.

Implement best practices through hands-on exercises and  experiments.

1. Understanding WCAG and CSS Accessibility

What is WCAG?

The Web Content Accessibility Guidelines (WCAG) provide a framework for creating accessible web content. WCAG is based on four principles:

Perceivable – Content must be presented in ways users can perceive.

Operable – Users must be able to interact with and navigate the site.

Understandable – Information and UI must be easy to understand.

Robust – Content must be compatible with assistive technologies.

CSS and Accessibility

CSS plays a crucial role in making content more accessible by ensuring:

Proper contrast and readability.

Clear focus indicators and keyboard navigation.

Responsive layouts that work across devices.

2. Practical Methods for Accessible CSS

2.1. Ensuring Readable Text

Font and Text Spacing

Use relative units (rem, em, %) for fonts to support zooming.

Ensure at least 1.5x line height (line-height: 1.5;).

Allow user preferences with font-size: 100%;.

Example:

css code

body { font-size: 100%; /* Allows browser settings */ line-height: 1.6; /* Improves readability */ }

Exercise 1:

Adjust font sizes and spacing in an HTML document.

Test with browser zoom (200%) and ensure content remains readable.

2.2. Providing Sufficient Color Contrast

Contrast Ratio Guidelines

WCAG AA requires 4.5:1 contrast for normal text, 3:1 for large text.

Use contrast checkers like WebAIM Contrast Checker.

Example of Good Contrast:

css

code

body { color: #222; /* Dark text */ background-color: #fff; /* Light background */ }

Experiment 1:

Use color contrast tools to check WCAG compliance.

Adjust CSS until you meet 4.5:1 contrast ratio.

2.3. Implementing Focus Indicators

        

Browsers provide default focus styles for keyboard users.

Use outline instead of border for better visibility.

Example:

css

 code

button:focus, a:focus { outline: 3px solid #ff9900; /* High visibility focus */ }

Experiment 2:

Remove CSS focus outlines and test keyboard navigation.

Re-enable outlines and customize them for better visibility.

2.4. Creating Accessible Hover and Active States

Do not rely on color alone for hover effects.

Use underline for links to indicate interactivity.

Example : code

a { text-decoration: none; } a:hover, a:focus { text-decoration: underline; background-color: yellow; }

Exercise 2:

Create buttons and links with clear hover and focus states.

Test using keyboard navigation (Tab key).

2.5. Responsive and Flexible Layouts

Use CSS Grid and Flexbox for adaptable layouts.

Avoid px for widths—prefer %, em, rem, min-width, max-width.

Example:

css code

.container { display: flex; flex-wrap: wrap; } .item { flex: 1 1 auto; min-width: 200px; }

Exercise 3:

Design a flexible card layout with CSS Grid or Flexbox.

Resize the browser and observe how it adjusts.

2.6. Hiding and Showing Content Correctly

        

Use visibility: hidden; instead of display: none; for screen readers.

Prefer aria-hidden="true" for decorative elements.

Example:

css

 code

.hidden { position: absolute; left: -9999px; }

 Experiment 3:

Test screen reader behavior on display: none; vs. aria-hidden="true".

3. Accessibility Testing and Validation

3.1. Manual Testing with Assistive Technology

Test with screen readers (NVDA, VoiceOver).

Check keyboard navigation using Tab and Shift + Tab.

3.2. Automated Testing Tools

axe DevTools – Chrome extension for WCAG audits.

Lighthouse – Google Chrome's accessibility scanner.

Experiment 4:

Run axe DevTools on a webpage.

Fix at least three accessibility issues.

4. Case Study: BBC Accessibility Guidelines

BBC enforces WCAG with:

         

        

High contrast mode.

Customizable text size.

Clear keyboard navigation.

Exercise 4:

Analyze BBC’s homepage for WCAG compliance.

List 3 good practices and 3 improvements.

5. Summary and Key Takeaways

Readable text: Use relative font sizes, proper spacing.

Contrast compliance: Ensure a 4.5:1 contrast ratio.

Keyboard-friendly navigation: Implement focus indicators.

Flexible layouts: Use responsive CSS techniques.

Proper content visibility: Hide elements correctly.

6. Final Assignment

Task:

Build a one-page website with:

WCAG-compliant contrast and typography.

Keyboard-accessible navigation and focus indicators.

Responsive CSS Grid/Flexbox layout.

Validate using axe DevTools and fix any accessibility issues.

This module ensures a practical, hands-on approach to mastering CSS accessibility.