HTML and CSS Reference
With the rapid evolution of web services and technologies, the number of Internet users is constantly increasing.
Since many people suffer from various temporary or permanent disabilities and deficiencies, advanced web
development practices should be applied to provide content that is accessible for all. The importance of web
accessibility is being recognized by an increasing number of web designers and developers. W3C provides useful
guidelines to ensure content accessibility. The accessibility support implemented in modern software tools and
web sites should be clearly indicated so people living with disabilities can easily identify them. HTML5 markup also
supports accessibility through advanced structuring elements, metadata, and Accessible Rich Internet Applications
(ARIAs). Web accessibility techniques are not limited to the visually impaired or people with other disabilities. In fact,
they also ease mobile access to web content and improve overall web page quality.
In this chapter, you will learn the criteria of accessible web sites, along with the techniques to fulfill them. You will
understand the concept of web accessibility and become familiar with the most widely adopted official guidelines.
The corresponding guidelines provide access to your web sites for the disabled and improve the user experience for
people using devices with limited hardware capabilities, such as mobile users. The content of your web sites should
remain legible even if the style sheets are turned off, can be read out loud effectively by screen readers, and rendered
also in text-based browsers such as Lynx. Moreover, the techniques that support accessibility have a nice side effect:
they improve web site usability and user experience as well.
Defining Web Accessibility
By default, web sites containing a variety of components, especially the ones with nontextual content such as
videos, cannot be used by all people. Even common web site components like text might be difficult, and sometimes
impossible, for some people to read. Not all users can see colors or move the mouse. Everybody knows how frustrating
a web site can be when it does not work or has functionality that is very difficult to use for whatever reasons. Now
imagine that feeling magnified by a factor of ten or a hundred, which is what people with disabilities suffer from when
using inaccessible web sites. The degree of frustration varies from person to person, because some people live with
visual impairment, while others with mobility, dexterity, auditory, or cognitive impairment.
More and more countries have introduced legislation addressing the need for web sites to be accessible to people
with disabilities or the requirement to be nondiscriminative against people with disabilities. Some examples are the
Disability Discrimination Act 1992 in Australia , the Disability Act 2005 in Ireland , the Disability Discrimination
Act 1995 in the United Kingdom , or Section 508 Amendment to the Rehabilitation Act of 1973 in the
United States .
Web accessibility covers those web site development practices that provide web content usable (“accessible”)
for everybody, including people with disabilities. W3C director Tim Berners-Lee announced the launch of the
International Program Office (IPO) for the Web Accessibility Initiative (WAI)  at W3C in 1997 by defining
accessibility as follows: “The power of the Web is in its universality. Access by everyone regardless of disability is an
essential aspect” .