上海时时乐组三技巧:Introduction to Web Accessibility

Accessibility in Context

The power of the Web is in its universality.
Access by everyone regardless of disability is an essential aspect.

Tim Berners-Lee, W3C Director and inventor of the World Wide Web

The Web is fundamentally designed to work for all people, whatever their hardware, software, language, location, or ability. When the Web meets this goal, it is accessible to people with a diverse range of hearing, movement, sight, and cognitive ability.

Thus the impact of disability is radically changed on the Web because the Web removes barriers to communication and interaction that many people face in the physical world. However, when websites, applications, technologies, or tools are badly designed, they can create barriers that exclude people from using the Web.

Accessibility is essential for developers and organizations that want to create high-quality websites and web tools, and not exclude people from using their products and services.

What is Web Accessibility

Web accessibility means that websites, tools, and technologies are designed and developed so that people with disabilities can use them. More specifically, people can:

Web accessibility encompasses all disabilities that affect access to the Web, including:

Web accessibility also benefits people without disabilities, for example:

For a 7-minute video with examples of how accessibility is essential for people with disabilities and useful for everyone in a variety of situations, see:
Web Accessibility Perspectives Video (YouTube)

Accessibility is Important for Individuals, Businesses, Society

The Web is an increasingly important resource in many aspects of life: education, employment, government, commerce, health care, recreation, and more. It is essential that the Web be accessible in order to provide equal access and equal opportunity to people with diverse abilities. Access to information and communications technologies, including the Web, is defined as a basic human right in the United Nations Convention on the Rights of Persons with Disabilities (UN CRPD).

The Web offers the possibility of unprecedented access to information and interaction for many people with disabilities. That is, the accessibility barriers to print, audio, and visual media can be much more easily overcome through web technologies.

Accessibility supports social inclusion for people with disabilities as well as others, such as:

There is also a strong business case for accessibility. Accessibility overlaps with other best practices such as mobile web design, device independence, multi-modal interaction, usability, design for older users, and search engine optimization (SEO). Accessible websites can have better search results, reduced maintenance costs, increased audience reach, and demonstrate corporate social responsibility (CSR).

Web accessibility is required by law in many situations.

Making the Web Accessible

Web accessibility depends on several components working together, including web technologies, web browsers and other "user agents", authoring tools, and websites.

The W3C Web Accessibility Initiative (WAI) develops technical specifications, guidelines, techniques, and supporting resources that describe accessibility solutions. These are considered international standards for web accessibility; for example, WCAG 2.0 is also an ISO standard: ISO/IEC 40500.

Making Your Website Accessible

Most of the basics of accessibility are fairly easy to implement. If you are new to accessibility, it takes some time and effort to learn the common issues and solutions.

Some accessibility barriers are more complicated to avoid. Some accessibility solutions take more time and effort to implement.

It is most efficient and effective to incorporate accessibility from the very beginning of projects and throughout organizations.

Evaluating Accessibility

When developing or redesigning a website, evaluate accessibility early and throughout the development process to identify accessibility problems early, when it is easier to address them. Simple steps, such as changing settings in a browser, can help you evaluate some aspects of accessibility. Comprehensive evaluation to determine if a website meets all accessibility guidelines takes more effort.

There are evaluation tools that help with evaluation. However, no tool alone can determine if a site meets accessibility guidelines. Knowledgeable human evaluation is required to determine if a site is accessible.

Examples

Alternative Text for Images

image of logo; HTML markup img alt='Web Accessibility Initiative logo'

Images should include equivalent alternative text (alt text) in the markup/code.

If alt text isn't provided for images, the image information is inaccessible, for example, to people who cannot see and use a screen reader that reads aloud the information on a page, including the alt text for the visual image.

When equivalent alt text is provided, the information is available to people who are blind, as well as to people who turn off images (for example, in areas with expensive or low bandwidth). It's also available to technologies that cannot see images, such as search engines.

Keyboard Input

mouse crossed out

Some people cannot use a mouse, including many older users with limited fine motor control. An accessible website does not rely on the mouse; it makes all functionality available from a keyboard. Then people with disabilities can use assistive technologies that mimic the keyboard, such as speech input.

Transcripts for Audio

example transcript

Just as images aren't available to people who can't see, audio files aren't available to people who can't hear. Providing a text transcript makes the audio information accessible to people who are deaf or hard of hearing, as well as to search engines and other technologies that can't hear.

It's easy and relatively inexpensive for websites to provide transcripts. There are also transcription services that create text transcripts in HTML format.

For More Information

W3C WAI provides a wide range of resources on different aspects of web accessibility standards, education, testing/evaluation, project management, and policy. We encourage you to explore this website, or look through the WAI Resources list.

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