With the rising usage of mobile devices and at least 4 different platforms (iOS, Android, Windows Mobile and RIM) the usage of web-based applications is becoming more and more popular due to the platform independence. Whereas application accessibility is supported by the desktop component of the operating system, web accessibility largely depends on the content itself and furthermore on the web browser application. In addition, as the web browser is itself a desktop application, desktop accessibility still has a critical part to play. Web accessibility depends on collaboration between the website, the browser, the desktop and any assistive technology being used. The World Wide Web Consortium (W3C) recognizes the importance of this. As part of its Web Accessibility Initiative (WAI) work (see [WAIH] ) it has produced a series of accessibility standards and guidelines that cover the web aspects. Of particular importance are the Web Content Accessibility Guidelines (WCAG) 2.0 [WCAG] which have been developed through the W3C process in cooperation with individuals and organizations around the world, with a goal of providing a worldwide harmonized standard for Web content accessibility that meets the needs of individuals, organizations, and governments internationally.
Web accessibility is reasonably straightforward in the case of websites that display content in fairly static pages. Here the requirement is to ensure that the content is well structured, can be easily navigated and may be presented in a way suitable for the user. This may be directly supported by features added to the site itself, such as provision of different text sizes. Alternatively, adaptation can be left to the browser, desktop or assistive technology, as long as the website design follows some basic good practice. The advantage of the latter approach is that user experience will be more consistent for all sites visited. However, not all sites are well designed and some may be impossible to adapt.
The so called 'Web 2.0' has seen a proliferation of Rich Internet Applications (RIAs), such as Gmail , which behave like desktop applications in the browser, e.g. in the mobile device. These require that web developers and web browsers work a little harder in order to provide similar support to that available on desktop applications. The main issues are that the user needs to be notified of unexpected updates to any part of the page. Also, assistive technology needs to be aware when web structures are re-purposed to create new types of interactive controls. For example, lists are often used to create dynamic menus. Fortunately, the W3C has recently released the Accessible Rich Internet Applications (WAI-ARIA) standard (see [WARIA] ) to address these requirements. Open source projects like Firefox and screen readers such as Orca and NVDA are at the forefront of support for these new technologies, with the commercial vendors following more or less closely.
The requirement for each web application to implement accessibility features is eased by using libraries or widget sets that have accessibility built in. These usually consist of HTML, JavaScript code and CSS style sheets that are used in the web browser along with some form of server side support. This greatly eases the web application developer's job and provides a more consistent user experience. Dojo and jQuery are popular examples of these accessible UI toolkits for creating RIAs. (See also [OAO] .)