I always feel a certain degree of scepticism when it comes to the concept of universality in Web design. My intuition and usability experience tell me, that a good universal solution does not really exist.
Any universal Web site, intended for use by both able and disabled people, can be easily improved, if we optimise it specifically for each target audience. On the other hand, we designers don't usually consider what is best and optimal for the disabled audience. Frequently, disabled people are just out of the picture when it comes to design and any provisions for that audience are generally an afterthought. Ironically, designers and Web masters may find themselves in need of better Web accessibility -- repetitive strain injury (RSI) hits the best of us.
This is just a short overview of the Web accessibility field and it is not intended to replace any official accessibility recommendations and guidelines.
Who are the disabled and how do they use a computer?
A partial list of audience disabilities that Web designers should consider includes: blindness; low vision; colour blindness; physical and motor disorders; cognitive, neurological and learning disorders; and epileptic seizure disorders (triggered by visual blinking).
Blind people hear textual information through a synthetic voice (text-to-speech) software. They also may use Braille output hardware. People with low vision usually increase system fonts. For example, they may use big yellow fonts on a black background. They may also use screen magnification software. People with physical and motor disabilities usually use special hardware like a head-mouse or a head-pointer, specialised keyboards, or voice recognition software.
How to improve accessibility of Web sites
Below is a list of my top 12 Web accessibility tips, sorted by project management importance:
Take note: This is not a full list. Please refer to W3C accessibility guidelines 1.0 for a more complete list.







Talkback
Just wanted to clarify - in your list of 12 tips you say:
"Use text presentation via ‹B›, ‹CENTRE›, etc."
I'm assuming you really meant to say something along the lines of "Do not determine text presentation via <B>, <CENTER>, etc..." as those tags:
1. are strictly presentation based, and text formatting and visuals should be done with CSS, and,
2. they provide no semantic logic or structure to the document.