Full Article: http://www.nfb.org/nfb/Target_Sept_Release.asp?SnID=35783695

What Makes a Site Accessible?

HTML, the language of the web, allows designers and developers to tag visual elements with text descriptions and give names to “clickable” items so that people who cannot see or cannot use a traditional keyboard and mouse can navigate a website.  Many sites can be made accessible by simply completing these alternative description and title tags.  Some sites that contain interactive, animated content may require redesign to remove interactive menus, text and links that is not compatible with text-to-speech screen readers and alternative input devices.  For more information on making websites accessible, please see the  Information Technology Technical Assistance and Training Center website.

What Makes a Website Inaccessible?

In short, laziness or lack of attention to detail.  HTML, the language the web is built so that a complete web page is accessible to nearly everyone.  For example, pictures have attributes that give a text description and text title.  The problem is that it takes costly designer or developer time to type in attributes and give titles to every bit of meaningful non-text content, so most site owners neglect properly “tagging” their site's content.  This is especially difficult for animations and video which requires a large expenditure of time to properly caption or in some cases, cannot be captioned at all.

Are there other Benefits to making your site accessible?

Search engines use the same information that is used for making a site accessible to persons with disabilities to help categorize and rank websites.  A site that is accessible often ranks higher for relevant and often used search terms than inaccessible sites.