The authors are not responsible for the content of any external sites linked to from webdesignbook.org
©2006–2012 MacAvon Media.
Answers to Exercises, Chapter 9
Buy Chapter 9, Web Accessibility, in PDF format: now available from the MacAvon Media Downloads Store.
- RSI can make it impossible to use the affected hand. Even in the absence of pain, it is advisable to avoid using an injured wrist because it will make matters worse. Use of a mouse is particularly liable to exacerbate an RSI condition – trackballs, trackpads and graphics pens are not much better, although changing among devices can provide some relief to specific affected parts. The result would be that you would have to avoid pointing, clicking and dragging with the mouse, and instead rely on keyboard input to control your computer. (If you are right-handed and try to use your left, your pointing will be erratic, so you will still have problems with the mouse that you didn't experience before.) Typing can, in itself, cause RSI, so you would also have to cut down on the amount of text you created, and probably slow down your typing. In severe cases, you would have to use a voice input device.
Web site features that would cause problems under these circumstances include links and form controls. If the site's designer has not taken care to ensure that all links and controls can be activated by the keyboard, you may be unable to make the site work without hurting yourself, or possibly not be able to use the site at all. Dragging scroll bars or turning a scroll wheel may be problematical for RSI sufferers, so moving about long pages without internal skip links will be difficult.
- The names for the conformance levels were chosen to make it easier for screen readers to speak them. (How would you pronounce 'AAA' if you didn't know?) Always aim for Triple-A conformance, though it can be very difficult to achieve. Never accept less than Double-A.
- Providing alternative pages is rarely the best way of making a site accessible, since these alternatives almost inevitably provide an inferior substitute for the original pages and tend to become neglected as the site is updates. The use of alternatives also suggests to people with accessibility problems that they are being treated as inferior visitors to the site. It should only be done when other methods fail. With the support for accessibility in XHTML, this is almost never going to happen.
- If markup is separated from presentation, the information about the document's structure is explicitly expressed in the markup, and not implicit in the particular way parts of the document are presented (for example, in large bold type). This means that these two aspects of the document can be processed independently. The structure is a property of the document's contents, and is required no matter how the content is presented to a user. The presentation depends on the particular way in which the document is being accessed. Visual presentation features, such as colour, positioning and fonts, only convey information via visual user agents, such as conventional browsers. If this is separated from the structure, non-visual user agents can make use of the independently specified structure to present the document in different media. For example, screen readers can speak the contents, using appropriate aural cues to indicate where sections begin, and so on. Alternative specifications of presentation can be substituted for the default. For instance, users who have trouble seeing can provide their own stylesheet that specifies large readable fonts and high contrast between text and backgrounds; stylesheets for aural presentation can be provided. If presentation and markup are bound up together, for example, by using
fontelements to indicate change of font, this sort of re-presentation using alternative stylesheets is not possible.
- What constitutes suitable alt-text for a particular image may depend on its context and how it is being used. Assuming the photograph is there for the sake of its content, something like 'Red berries on a rowan tree' is a suitable textual alternative. The diagram could have the alt-text 'Diagram showing layered protocols'. Notice that, whereas in the first case you do not need 'Photograph of...', for the diagram it is helpful to indicate that the picture is diagrammatic in nature. In the case of the diagram, a longer textual description, possibly linked to by a
longdescattribute but better included in the page's text, should also be available.
altattribute should never be omitted – it is required in valid XHTML. If the image is purely decorative, and a textual alternative would only be distracting to screen reader users, the attribute should still be included, but its value should be the empty string.
- Avoiding time-based media is certainly not desirable. A significant number of Web sites exist whose sole purpose is to present time-based media. In some cases, the use of animation, sound or video can enhance a site's accessibility by making it easier to understand by people with certain sorts of cognitive problems. In many cases, a judicious use of time-based media will help a site get its message across to all users. However, there may be a considerable amount of work involved in satisfying all the WCAG accessibility criteria for time-based media. Not all the criteria apply to all cases, and sometimes it may be fairly easy to supply the necessary alternatives. For instance, if a transcript of a talk that is presented on the Web as a movie has been prepared for a press release, incorporating it on the Web site should be straightforward. In more difficult cases, if your resources do not permit you to take the necessary steps to provide captions and transcripts, and no other alternative will provide the same information, it may, strictly speaking, be necessary to omit time-based media in order to satisfy accessibility guidelines. In practice, though, given the desirability of retaining the time-based media, it will often be necessary to arrive at some compromise. For example, simply providing an indication that a video clip has been embedded in the page, and a short description of its contents, may be adequate, depending on the material in the video. (Note that, in an ideal world, the job of extracting information from time-based media and presenting it in an alternative form would be carried out automatically by user agents, and work is in progress to make this happen, but it is not likely to bear fruit in the near future.)
- There is one simple way to ensure that pages do not present problems for people with defective colour vision – and at the same time to make them more easily readable by people with other visual problems – and that is to make sure that there is good contrast between text and its background. As we show in this chapter, this will ensure that even elements in confusible colours such as red and green are visible to everyone. The best way to check is by using a utility that simulates pages' appearance to people with different sorts of colour defect. If you cannot find such a utility, setting your monitor to greyscale provides an immediate impression of the contrast on the screen.
- (It isn't always easy to explain why something is a bad idea to a client whose heart is set on it.) You need to explain that flashing elements on a page can cause epilepsy-like fits in people suffering from photo-sensitive seizure disorders, and that these fits can have serious effects. You should also mention that flashing buttons will have a distracting effect, which will detract from the page's content for all visitors to the page, and may cause confusion and possibly distress in people with some sorts of cognitive disorder.
- The only way you can ensure that no font substitution will take place is by using an image of the text instead of including the characters in the marked-up document. The content of the image cannot be read by screen readers, so if such images are used as links in the navbar without some alternative being supplied, screen reader users would be unable to navigate the site. To avoid this problem, use the
altattribute of the
imgelement to provide a textual alternative for the links. (XHTML requires this attribute to be present; you must ensure that its value is suitably worded to provide a suitable alternative to the image. For images consisting only of rendered text, this is easy.)
- A good choice for the link text would be something like 'Read more about X', where X was a brief summary of the article's content. Alternatively, you could repeat the article's title, and add 'continued...', although this is not quite so perspicuous. What you must avoid is using exactly the same expression, such as 'More...' as the text for every link, because screen readers may create a list of links to enable a user to scan all the links without reading the full text of the page. This means that it must be clear from the link text in isolation roughly what each link points to. A collection of a dozen links all of which say 'More...' offers no clues as to which might be worth following and is therefore worthless out of context.
Discussion Topics: Hints and Tips
- Generally, you will only hear these arguments from people who don't know much about disabilities. Therefore, the best way to counter the proposition is by showing that disabled people are not helpless. Explain how assistive technology can be used to present content and facilitate interaction, and how XHTML provides features that work with assistive technology to enable sites to be perceivable, operable and understandable by all users. Explain that a lot of visitors to the site (including many of the relatively wealthy over-45 group) will have some problems with their eyesight, and will leave if they have trouble reading a page, so paying attention to accessibility in the visual design of the site is important. As we have stated repeatedly, making a site accessible makes it more usable by everybody, so that it retains more visitors, and this is sound business sense. It is worth thinking carefully about the answer to this question, because if you simply consider accessibility to be an unconditionally good thing, without examining why, you may be wrong-footed when you come across a client who demands that you justify your insistence on accessible Web sites.
- This article on accessites.org presents both points of view on the question of whether to hide skip links. Another article by the same author expands some of the points and relates the discussion to WCAG2.0. A search for 'skip links' on Google will lead you to expositions of different techniques for hiding links. Some experts hold that, with the capabilities of current screen readers, skip links are unnecessary. Certainly, it is generally agreed that they ought to be unnecessary, but user agents are not always as helpful as they should be. See how well any screen reader you have access to (including the free ones, such as VoiceOver or Firevox) handle this.
Practical Tasks: Hints and Tips
- Refer to Guideline 5 of WCAG 1.0 and the associated techniques as a specification of what is required.
- Another accessites article provides a good account of what can be done by automatic checking and what needs to be done manually. TAW is an alternative to the now-defunct Bobby for doing the preliminary automated checks.