Specific Barriers to Web Access

The purpose of this document is to help web designers understand how specific types of disabilities and their technical accommodations can raise barriers to web accessibility.

In many cases, adaptive technology is already available to address the accessibility issue, so the web publisher need not (and in some cases should not) attempt to duplicate that technology. However, adaptive technologies themselves can cause significant changes in the way that information is read from a computer screen. Web designers need to be aware of how adaptive technology affects access to their pages so they can consider this information when making design decisions. Many potential accessibility problems can be avoided by designing pages in ways that are already considered to be "good style" on other grounds.

Table of Contents by Disability

Difficulty coordinating fine muscle movements in hands and/or eyes.
Cognitive, learning or developmental impairments.
Deaf with American Sign Language as native language; English as second language.
Hearing Impaired; cannot hear audio.
Difficulty seeing small things.
Difficulty seeing in conditions of low-contrast.
Cannot distinguish colors - various specific problems.
Blind (moderate to complete vision loss).

1. Difficulty coordinating fine muscle movements in hands and/or eyes.

Broad range of disabilities, including repetitive strain injuries, cerebral palsy, arthritis, quadriplegia, and other disabilities.

Adaptive Technology or Strategy

Use mouse with difficulty.
Operating system or other software provides special keyboard commands to substitute for mouse movements.
Cursor control by special adaptive input device.
Speech recognition software.

Web Issues

The greatest problem associated with this disability and its adaptive technology is difficulty in guiding the cursor with precision. If links or hot images are too small (some guidelines recommend .5" by .5" as the minimum size), the user will miss the target.

Questions to consider:

How large are the link "targets" on your pages at various screen resolutions?
Users with mobility impairments cannot afford wasted motion, and the general public doesn't like it either. Does the design of your page force the user to jump around a lot from place to place on the screen in order to read it or navigate it?
Some forms are not accessible without a mouse. If you provide forms to gather data from users, do you provide alternative methods such as phone and/or fax numbers, printable forms and a mailing address?

2. Cognitive, learning or developmental impairments.

Adaptive Technology or Strategy

Screen reader with speech synthesis (see Blind).

May prefer to use graphics as a source of information when possible because of difficulties with written English.

Web Issues

In the international world of the web, many non-disabled users do not possess native skills with English.

Questions to consider:

If icons are used for navigation, is their meaning clear? Are they used consistently?
Are colors used consistently in your web pages? Do they assist in or detract from navigating your web site?

3. Deaf with American Sign Language as native language; English as second language.

Adaptive Technology or Strategy

May prefer to use graphics as a source of information when possible because of difficulties with written English.

Web Issues

If icons are used for navigation, is their meaning clear? Are they used consistently?
Are colors used consistently in your web pages? Do they assist in or detract from navigating your web site?

4. Hearing Impaired; cannot hear audio.

Adaptive Technology or Strategy

Relies on text and graphics for information.

Web Issues

Many non-hearing impaired users own computers that still do not have speakers of a high enough quality to project understandable speech or enjoyable music.

Questions to consider:

Do your pages provide transcriptions and descriptions of all audio clips and real-time feeds?
If you have video+audio clips or feeds on your page, are transcripts, descriptions, or captions available? (QuickTime provides a means of coordinating audio and video in order to provide synchronized captioning.)

5. Difficulty seeing small things.

Adaptive Technology or Strategy

Glasses.
Large monitor.
Browser configured to display large type.
Screen enlarging software.

Web Issues

Because the technology for magnifying information displayed on a computer screen is widely available, it can actually be counterproductive to design a web page with large fonts in order to accommodate this population.

Questions to consider:

Is your web page still readable with the browser configured to display very large font sizes?
Is your web page still readable with the screen palette set to 256 colors?
As the user increases the degree of magnification, the amount of viewable space grows smaller, and it becomes easy to "get lost" on the page because the borders are outside the viewing space. Are navigational menus, buttons or links in a standard and consistent position on each of your pages?

6. Difficulty seeing in conditions of low-contrast

Adaptive Technology or Strategy

Browser configured for higher contrast.
Operating system configured for higher contrast.

Web Issues

Does your web page still convey the information you want when it is viewed with black text on a white background?
Are the images on your page low- or high-contrast? It might help to provide a text-based description, particularly for navigational images that are low in contrast.
Many people have difficulty interpreting text and images that do not contrast enough with their background. Do you think most people would find your page "readable" with its current color scheme?
Is your web page still readable with the screen palette set to 256 colors?

7. Cannot distinguish colors - various specific problems

Adaptive Technology or Strategy

Some perceive color differences based on saturation and brightness more than on hue.

Saturation: Intensity of a color; the lighter it is the less saturated it is.
Brightness: Percentage of black in a color; more black makes a color less bright.
Hue: The color category; for example, the hue red contains many different "shades" of red.

Web Issues

The general population shows variation in its response to color. Many non-disabled people find it unpleasant to view certain colors side by side with other colors.

Questions to consider:

Do you use blue/yellow and red/green combinations on your web pages?
When it is important for two colors to be distinguished on your web pages, do you provide supplementary text?
If you use colors for navigation, do they vary in terms of brightness and saturation as well as hue?
How does your page look when displayed in gray scale?

8. Blind (moderate to complete vision loss).

Emerging Technologies - Web Issues

As the Web matures, new helper applications, search and indexing tools, and intelligent agents will be created to assist the general population in managing data found on the Web. Applications written to the HTML 3.2 specification will produce unpredictable and erroneous results when used to manage web pages that do not conform to the specification.

Do you use HTML tags according to the HTML 3.2 specification, or have you misused some tags in order to achieve certain effects that were otherwise unavailable to you?

Braille - Web Issues

Although Braille display devices are available, they are too expensive for most people to own. Not all blind people know Braille, but those who want to use it usually download text files and then convert them to printed Braille.

If an image is important to the understanding or appreciation of your web site, do you have an adequate text description of it available?
Many non-blind as well as blind users may want to print or download your pages. How easy is it to download or print out your site as a whole?
Not everyone enjoys installing and learning to use additional software, and many such products are inaccessible to blind people. If you provide downloadable files in non-HTML formats (like .pdf files), do you provide the same information in a text or HTML format? If the file is compressed, is it self-extracting?
Blind people, people using text-only browsers and people who have turned off automatic downloading of images see no useful information when a web page contains no text. Does the home page of your web site contain text that could guide such a user to a non-graphical alternative?
Do you provide text descriptions for video clips and video feeds?

Screen Readers

Screen Reader with speech synthesizer technology is more widely used than Braille, and it usually has many features. Below is a list of Screen Reader features and the Web Issues associated with them.

Sequential Reading

Screen Readers read sequentially from top to bottom, left to right (they are easily confused by columns).

As speech synthesis technology matures, browsers designed specifically to read HTML will make greater use of HTML tags to format output and provide options for the user. Tags that are used not according to the HTML 3.2 specification will create problems for such browsers.

Does your site have tables that do not "read" from top to bottom, left to right? This includes the use of tables to achieve the effect of columnar text layout. If so, is the information alternatively provided in some other non-columnar format?

Immediate Start

Screen Readers begin reading as soon as the page is loaded.

Do you have excessive standard text or navigational tools that appear at the top of every page? It is difficult for a speech synthesizer to be manipulated to "ignore" such items.

Navigation

Navigation is by link, word, line or character, but not by sentence or paragraph.

If a user hops from link to link on your web page, will she or he hear "click here" repeated over and over again or is the link text brief but meaningful?

Images

Screen Readers read content of ALT attributes with images but cannot interpret images themselves.

Do you use brief but meaningful ALT text with all images? Does your ALT text describe the function of certain visual images rather than just a description of the image? (Example: "change of topic" rather than "blue line")
If an image is important to the understanding or appreciation of your web site, do you have an adequate text description of it available?
Blind people, people using text-only browsers and those who have turned off automatic downloading of images see no information when a web page contains no text. Does the home page of your web site contain text that could guide such a user to a non-graphical alternative?
Do you provide text descriptions for video clips and video feeds?

Background Wallpaper

Screen Readers cannot interpret background graphical wallpaper (because there is no ALT attribute).

Do you use background images that contain important content? If so, do you provide an alternate (text-based) method for viewing that content?

Blinking Text

Screen Readers cannot reliably read blinking text (sometimes they skip it and sometimes they fixate on it).

Many non-blind people object to blinking text on aesthetic grounds, and it can affect speech synthesizer software negatively as well. Do you really need to use it?

Search and Punctuation

Screen Readers can search for text strings or attributes (jumping from link to link is accomplished by searching for underlined text). They use punctuation (periods, commas, etc.) to structure speech output.

In addition to its negative consequences for speech synthesis software, incorrect use of punctuation and spelling irritates many members of the general public. Do you use punctuation correctly and consistently throughout your site? Have you checked your spelling?

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Last updated 18-Feb-97.