Web accessibility means that people with disabilities can perceive, understand, navigate, and interact with the web, and that they can contribute to the web. Web accessibility also benefits others, including older people with changing abilities due to aging. Web accessibility encompasses all disabilities that affect access to the web, including visual, auditory, physical, speech, cognitive, and neurological disabilities.

Millions of people have disabilities that affect their use of the web. Currently most Web sites and Web software have accessibility barriers that make it difficult or impossible for many people with disabilities to use the web. As more accessible web sites and software become available, people with disabilities are able to use and contribute to the web more effectively.
Web accessibility also benefits people without disabilities in certain situations, such as people using a slow Internet connection, people with "temporary disabilities" such as a broken arm, and people with changing abilities due to aging.

So it is the duty of the website development companies to develop the websites to be accessible to all sections of people including disabled, old age, temporary disabled etc…The accessibility barriers to print, audio, and visual media can be much more easily overcome through web technologies. And also current laws and policies require Web accessibility to all.

One of the roles of the Web Accessibility Initiative (WAI – http://www.w3.org/WAI/) is to develop guidelines and techniques that describe accessibility solutions for Web software and Website developers. These WAI guidelines are considered the international standard for web accessibility.

Making a Web site accessible can be simple or complex, depending on many factors such as the type of content, the size and complexity of the site, and the development tools and environment.

Many accessibility features are easily implemented if they are planned from the beginning of Web site development or redesign. Fixing  an accessible Web sites can require significant effort, especially sites that were not originally "coded" properly with standard XHTML markup, and sites with certain types of content such as multimedia.

When developing or redesigning a site, evaluating accessibility early and throughout the development process can identify accessibility problems early when it is easier to address them. Simple techniques such as changing settings in a browser can determine if a web page meets some accessibility guidelines. A comprehensive evaluation to determine if a site meets all accessibility guidelines is much more complex.

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.

All website developers should be trained to be aware of all aspects of website accessibility so that they can evaluate, redesign and implement their procedures to create an accessible website.