When we say a site is accessible, we mean that the content is available to all, and can be operated by absolutely anybody.
Web accessibility is the inclusive practice of ensuring there are no barriers that prevent interaction with, or access to, websites on the World Wide Web by people with disabilities. When sites are correctly designed, developed and edited, generally all users have equal access to information and functionality.
Web Content Accessibility Guide - lines (WCAG) 2.0 is a set of best practices put together by experts to address exactly what "accessibility" means, and how to deliver it. WCAG is organized around four principles, often referred to as POUR:
• Perceivable: Can users perceive the content? Just because something is perceivable with one sense, such as sight, that doesn't mean that all users can experience it.
• Operable: Can users navigate the content? A hover interaction, for instance, cannot be operated by someone who can't use a mouse or touch screen.
• Understandable: Can users understand the content? Is the interface clear, and consistent enough to avoid confusion?
• Robust: Can the content be consumed by a wide variety of user agents (browsers)? Does it work with assistive technology?