What is an accessible website?

First of all, let's see what an accessible website is. An accessible website provides alternative means of understandnig its content. This implies that to everything that an impaired visitor can't see, a text alternative should be presented. This makes navigating and understanding the site much easier, for sighted visitors as well.

The benefits

The benefits of website accessibility, then are:

• a wider coverage of your target audience (about 10% of Internet US population is with disabilities (50kb, PDF)
• improved search engine visibility (search engines can't see and value text as well)
• greater convenience for non-impaired visitors by easier site navigation

This means that with an accessible website you not only increase your target audience and thus advance way far over your competitors among people with disabilities, but also gain a boost in the search engine traffic for the ordinary visitors as well.

Speaking of search engine visibility. Recently, Google launched Google Accessible Search for people with disabilities. The search is intended to grant special value to accessible websites. To put simply, this is a vehicle to make the above benefits more real.

Legal requirement in US, UK and Europe

Also, website accessibility has long become a legal requirement in US, UK (PDF) and will be legal in Europe. Not that every person that is disgusted by your site accessibility will sue you, but the possibility remains if you are a popular website or provide something that everyone (even the poor-sighted people) can and will use.

How to make a site accessible?

Here are a couple of quotes from the Google Accessible Search FAQ:

It tends to favor pages that degrade gracefully --- pages with few visual distractions and pages that are likely to render well with images turned off.

Broadly, Google defines accessible websites and pages as content that the blind and visually challenged can use and consume using standard online technology...

Currently we take into account several factors, including a given page's simplicity, how much visual imagery it carries and whether or not it's primary purpose is immediately viable with keyboard navigation

Judging from the quotes above, and from Web Content Accessibility Guidelines, here is what you can do to improve your site accessibility:

• provide text alternative for any media (images, auto, video)
• provide alt and title attributes to images and links (alt attribures require shorter descriptions, while titles may be longer)
• replace text in images with styled text (this will make your site load faster as well)
• use simple language that your visitors can understand
• use valid, semantic HTML markup (validate your pages and use headings and subheadings properly)

Summing up

Generally, a good website usability analysis will make a website accessibile (Priority 1 or Section 508 compliant, for instance). However, if you want your site to be absolutely accessible for people with disabilities, you'd rather get someone specifically just for this mission.