HTML and CSS Reference
Chapter 6. Accessibility
The Web has the potential to more fully integrate people with seeing, hearing, physical, learning, and other
disabilities into society. By limiting the interaction necessary to communicate, as well as enabling delayed
communications so that participants can move at their own pace, the Web has transformed our relationships
with one another. Properly designed web pages neither know nor care whether you're reading them with a CRT
or a screen reader. Properly designed forms neither know nor care whether you're inputting data with a
keyboard, a mouse, or voice recognition software.
However, accessibility does not come automatically. Many pages are locked into one modality of use, most
commonly visual. Many pages are designed with the assumption that the user will view the page in the same
way the designer does. Such pages can lock out people with different levels of eyesight, attention, motor skills,
and a dozen other characteristics.
Accessibility is not just about supporting people with extreme physical impairments such as blindness either.
Ability and accessibility are both continuums. People don't merely see or not see. They see better or worse.
Most of us see worse with age. By age 40, we've either discovered the Ctrl-+ keyboard shortcut for increasing
the font size of our browser or we've begun to curse 20-something web designers as we surf (or both). The
changes you make to improve accessibility don't just help people who meet the legal definition of disabled . They
help everyone whose seeing, hearing, or motor skills are less than perfect. At least some of the time, that's all
of us. If it isn't today, it will be tomorrow. As we age, eyesight and motor skills decline, and accessibility
becomes more important. When I started on the web, college students represented a majority of the population
on the Net. Today they're probably less than 10%, and they are vastly outnumbered by senior citizens.
Accessibility also improves your site for people accessing it with nontraditional devices. A 28-year-old Wall
Street trader may prefer to view your news through the small screen of her BlackBerry. Even an airline pilot
with 20/20 vision may as well be blind when listening to your page on his cell phone while jogging.
Of course, accessibility isn't just about supporting people with physical or device impairments. Wheelchair
ramps are far more commonly used by parents with strollers, students with bicycles, and delivery people with
hand trucks than they are by people in wheelchairs. When properly done, increasing accessibility for the
disabled increases accessibility for everyone. That's as true on the World Wide Web as it is in the physical world.
In many jurisdictions, accessibility is not just a good idea. It's the law. In the United States, the Americans with
Disabilities Act requires that all web sites built or procured by the federal government be accessible to users
without regard for physical handicap. In the United Kingdom, the Disability Discrimination Act imposes similar
requirements, and many other nations either already or soon will have equivalent laws.
If all that isn't enough to convince you that it's important to invest time and resources in making your pages
accessible, consider this. The most profoundly disabled user of your page is going to be a search engine robot.
Robots can't see, hear, touch, or think. They are unbelievably stupid. Although a person can eventually make
sense out of a strange layout or text encoded in an image, a robot never will. Almost everything you do to make
your pages more accessible to and usable by people will be paid back tenfold in search engine optimization.
Simply making documents valid XHTML makes documents a lot more accessible than they otherwise would be.
Making them strict XHTML rather than transitional goes even further. Removing presentational elements such as
b and replacing them with semantic elements such as strong helps a little. Separating the content from the
presentation using CSS stylesheets helps a lot.
However, that's the beginning of accessibility, not the end. If you aren't careful, you can create completely valid
but almost totally inaccessible pages. Validation is an automatic and unthinking process. It focuses purely on
the syntax. It can't tell whether you've chosen green or red text that will be impenetrable to many color-blind
visitors. It doesn't know that the first 20 KB of your page are advertising and navigation that blind users have to
slog through before getting to the actual content. It can't distinguish between a well-designed data table
containing monthly financials and a layout table that rearranges the linear flow of text into unintelligible