COMP 135Web Site Design

IntermediateWeek 7

Accessibility Definition, policies, standards

Continuum of abilities

What is Web Accessibility?

The practice of making web sites usable by people of all abilities and disabilities

Correctly designed web sites provide everyone with equal access to information and functionality

It is a human right and a moral obligation

Understanding Accessibility Visual Impairment

• Ranges from complete blindness, to low vision, to colour blindness

Mobility or Dexterity Impairment• Severe: paraplegia/quadriplegia, cerebral palsy,

multiple sclerosis• Difficulty with fine-motor: arthritis, Parkinson’s

Disease• Old age

Auditory Impairment• Deaf, hard of hearing

Cognitive Impairment• Severe learning disabilities, low literacy or numeracy

skills, dyslexia, cultural or language differences

Visual Impairment People who are blind can use

computer but they can’t see the screen

People with low vision may only see the screen partially

People with colour blindness cannot distinguish some colour combinations because of low contrast

Mobility or Dexterity Impairment

Limited arm movement

Use of only one hand

Difficulty controlling fine movements

Difficulty holding a mouse

Tremors, shaking hands

Auditory Impairment Sure, a deaf person can watch a

video, but how meaningful is it without the audio?

Cognitive Difficulties Memory-related

Problem-solving

Attention deficits

Reading, linguistic and verbal comprehension

Math comprehension

Visual comprehension

Assistive Technologies Hardware

• Touch screens• Head- and mouth-wands• Switches• Customized keyboards• Large mice• trackballs

Software• Screen readers• High contrast colour schemes• Text and icon magnification

Web Content Accessibility Guidelines (WCAG 2.0)

W3C standard, approved December 2008

Provides set of principles and guidelines that you should be familiar with before building a web site

Consists of four principles and broken down into 12 guidelines

Each guideline has several “success criteria”

Levels of Conformance A – This is the lowest level and

means you’ve met the minimum level of accesibility

AA

AAA

Guiding Principlesand Guidelines

1. Perceivablea. Provide text alternatives for any non-text contentb. Provide alternatives to time-based mediac. Create content presentable in different ways

without losing structure or informationd. Make it easier to see and hear content

(background/foreground contrast

2. Operablea. Make all content accessible by keyboardb. Provide enough time to read contentc. Do not design content that could cause seizures

3. Understandablea. Make text content readable and

understandableb. Make web pages that operate predictablyc. Help users avoid and correct mistakes

4. Robusta. Maximize compatibility with current and

future user agents and assistive technologies