Using Style Sheets to Enhance Accessibility for People with Low Vision or Cognitive Disabilities


Maximum Accessibility: Making Your Web Site More Usable for Everyone
By John M. Slatin,, Sharron Rush
Table of Contents
Chapter 15.  Supporting Accessibility with Cascading Style Sheets

In this chapter, we use CSS to address some of the problems that people with cognitive disabilities or low vision might encounter when using the AIR judging form. Before we discuss the design, however, let's take a look at the terms low vision and cognitive disabilities.

Low Vision

The term low vision covers a very broad range of conditions. The number of people who have partial or limited vision far exceeds the number of people who have no useful vision at all. There is a substantially higher incidence of low vision among people over 50 than in the general population, resulting from such conditions as macular degeneration, glaucoma, and diabetic retinopathy, which often worsen with age. According to Jupiter Research, people over 50 represent a larger number of users (23,000,000 by the end of 2000) than kids, teens, or college students. [1] And people over 65 form the fastest-growing group in the population as a whole. So designers can expect more and more people with limited vision to visit Web sites.

[1] Cited in "Jupiter Research Digital Divides," accessed December 1, 2001, at

People with low or limited vision tend to benefit from larger, simpler, open fonts such as Arial, Verdana, Geneva, and other sans-serif typefaces (this book, for example, uses 14-point Minion). They also benefit from clearly contrasting colors. Some users set their browser or system preferences to use large font sizes; some rely on screen magnification software such as AI Squared's ZoomText or Freedom Scientific's Magic. Others use both techniques. As we noted earlier, sophisticated users can even specify their own style sheet to override the designers' styles to modify background and font color, font size, and other properties to meet the users' particular needs. But many people with limited vision especially elderly users don't think of themselves as having disabilities or don't realize they can customize the software they use (or both).

Cognitive Disabilities

The term cognitive disabilities also covers a huge range of conditions. Many of these conditions are difficult to quantify or even to detect, and for that reason they are sometimes called hidden or invisible disabilities. But whether you can see them or not, they are very real.

People who have cognitive disabilities such as those associated with ADD or caused by TBI may view the screen at a standard resolution (such as 800 x 600). But they, too, may find "busy" pages and complicated layouts difficult or even impossible to use. Like people with limited vision, people with ADD or TBI may have trouble distinguishing foreground images and text from background material. Or, faced with a large number of options, they may have difficulty recognizing the choice most appropriate to their needs at the moment.

Some people with cognitive impairments use assistive technology that guides their attention by masking many of the elements on the screen or highlighting the element that currently has the focus. People with reading disabilities such as dyslexia may use assistive technology that combines masking techniques and screen-reading software for simultaneous visual and auditory input. But such technologies are beyond the financial reach of many individuals and many cognitive disabilities go unrecognized and undiagnosed.

Style Sheets and Conflicting Needs

The AIR judging form might present problems for both groups. The items on the AIR judging form we explored in Chapter 10 may be too densely packed for a judge with ADD or TBI to negotiate successfully. Similarly, someone with limited vision may have trouble recognizing where one section or item ends and the next one begins.

There is some evidence to suggest that design solutions that satisfy the needs of users with low vision may cause problems for users with cognitive difficulties, and vice versa. This doesn't mean that you, as a Web designer, should just throw up your hands! This is the very kind of dilemma that style sheets are designed to resolve. We'll try to find a solution that works for everyone; if we can't, we may be able to use CSS to let users themselves choose the alternative that works best for them.


    Maximum Accessibility(c) Making Your Web Site More Usable for Everyone
    Maximum Accessibility: Making Your Web Site More Usable for Everyone: Making Your Web Site More Usable for Everyone
    ISBN: 0201774224
    EAN: 2147483647
    Year: 2002
    Pages: 128

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