17-05-2014, 02:28 PM
Understanding Web Accessibility
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INTRODUCTION
At the most basic level, web accessibility is about people being able to get and use web content. It is
about designing web pages that people can present and interact with according to their needs and
preferences. A primary focus of accessibility is access by people with disabilities. The larger scope
of accessibility includes benefits to people without disabilities. While accessibility is presented here
in its relationship to usability, it is important to remember that the fundamental point is the ability to
access web content at all. What is nice to have for some people is required by other people for them
to be able to access web sites at all.
This chapter introduces web accessibility, with a focus on the synergy between usability and
accessibility. It covers the benefits of accessibility, beyond access for people with disabilities. Some
common myths are addressed and the conclusion touches on opportunities related to web
accessibility. References for more information are included throughout the chapter text and in a
reference list at the end.
Usable Accessibility
While many would agree with the concept of accessibility being related to usability, that is often not
how accessibility is approached in practice. Many designers and developers were recently
introduced to accessibility because of regulations such as Section 508 of the Rehabilitation Act in the
US. In such cases, the focus of accessibility is often limited to meeting standards and guidelines.
Often this means technical aspects get emphasized at the expense of the human interaction aspect.
(This problem can also be seen in some assistive technologies and early web sites that were
developed specifically for people with disabilities. While being accessible to some, they
demonstrated a clear lack of usability.)
A simplified example of something that can "pass" an automated check for accessibility and still not
be usable is alternative text for an image (adding an alt attribute to the <img> element that
describes the graphic; there's more about this below). Alternative text can be provided that does not
help users without access to the image at all. The alt text must be meaningful in the context of the
page for the page to be usable without images.
This problem can be avoided by adopting the broader definition of accessibility as a guiding
principle. Instead of focusing only on the technical aspects, it is important to recognize that usability
is also an important aspect of accessibility. Consciously addressing 'usable accessibility' helps to
clarify the difference between what meets minimum accessibility standards and what is usable by
people with disabilities.
Differentiating Between Usability and Accessibility
When designing web sites, it is rarely useful to differentiate between usability and accessibility.
There are times when such a distinction is considered, such as when looking at discrimination
against people with disabilities and when defining and addressing specific accessibility standards
and guidelines. The following problems illustrate the difference between usability and accessibility:
Usability problems impact all users equally, regardless of ability. That is, a person with a
disability is not disadvantaged to a greater extent by usability issues than a person without
a disability.
Accessibility problems hinder access to a web site by people with disabilities. When a
person with a disability is at a disadvantage relative to a person without a disability, that is
an accessibility issue.
Functional and Situational Limitations
The Differentiating Between Usability and Accessibility section distinguished accessibility as related
to disability. Subsequent sections showed areas where this distinction is blurred. A broader definition
of accessibility, provided below, is more suitable in most circumstances.
Accessibility can be defined as the quality of a web site that makes it possible for people to use it –
to find it navigable and understandable – even when they are working under limiting conditions or
constraints.