Accessibility
is a general term used to describe the degree to which a system is
usable by as many people as possible. Accessibility can also be viewed
as the "ability to access" the functionality, and possible benefit, of
a website. Websites that are not accessible would make access difficult
for people with poor eye sight through to major visual impairments and
blindness, colour blindness, dyslexia, epilepsy (flicking), motor
skills impairment; or people with old computers and browsers, or older
plugins and software.
Accessible websites may have re-sizable text; the ability to use your
own stylesheet (text and background colour combinations); shorter line
lengths on text; well spaced links, access keys or tabbing; alt tags
for screen readers; semantically sound, text only versions of pages;
and would avoid having animations that flicker too much or move very
fast; or colour combinations like red text on green pages.
Many improvements made to websites to make them more accessible, result
in them being better for all users, so the benefits reach everyone.