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Computing and Information Services

Demonstration of Inaccessibility

The examples in the Inaccessibility Demonstration are each intended to demonstrate a common accessibility error, but in a way that affects a different set of people to the normal set.

Example 1: Frames

To find the link to the next stage in this example, you need to have a browser that does not display frames by default. An exhaustive list of browsers that will pass is impossible, of course, but the following browsers will work fine:

  • Lynx, Links (any version)
  • Netscape (version 1 only)
  • Opera with frame support disabled (any version)
  • w3m with automatic frame rendering off
  • Mosaic (any version)

If your browser supports frames and does not have an option to disable them, then you will not be able to get past this page. Of course, the usual situation is that users with browsers that do not support frames cannot get past the first screen.

Recommendations for accessible use of frames.

Example 2: Javascript

This example will only display the link to the next page if Javascript is disabled or not present. You should be able to disable Javascript if your browser supports it to view this page anyway (although disabling Javascript in Internet Explorer is more difficult than it should be).

The normal situation is that Javascript is required to view the site. Some users will be able to enable it (if they really want your information), but others will be using browsers with no Javascript support and unable to obtain browsers that do.

Recommendations for accessible use of scripts and applets.

Example 3: Document Relationships

Despite having been in the HTML specification for over five years, very few browsers support this useful feature. If this feature is relied on for navigation, then you cannot navigate the site. However, if used in addition to normal links, it improves navigation for users with browsers that support it.

This is supported by:

  • Mosaic 3 (windows only)
  • Lynx (recent versions)
  • Mozilla (recent versions) and some browsers based on it (e.g. Galeon)
  • Opera 7

There are many features like this, including images, java applets and image maps, that can enhance usability and accessibility if used well. However, alternatives must be provided for browsers that do not support them.

Example 4: Auto-refreshing

This page automatically refreshes itself to stage 4a, after one second. This makes it impossible to use or read. For reference, the text is:

If you can read this, your browser probably does not support (or allows you to disable) page refreshing. Either that, or you are a really fast reader. Next page.

Page redirection using 'meta refresh' should be avoided where possible. Where it is used, an alternate text link must be provided.

Refreshing a page to itself can have serious problems. Imagine the situation of a slow reader on a page that refreshed every minute. It shouldn't be too difficult having been through this page.

As you have seen in the demonstration, refreshing a page can cause problems for slow readers, and can be disorientating for everyone. Using the same technique to redirect to another page is not as bad, but is still better avoided where possible.

You should be able to read this page easily with:

  • Most text mode browsers (lynx, links, w3m, etc)
  • Mosaic (though you may need to change the configuration slightly)
  • Pressing the shortcut key or icon for 'View Source' quickly enough.

Example 5: Browser-specific instructions

Giving browser specific instructions can cause a usability problem. The instruction in this example only makes sense in some text browsers (lynx and links, but not w3m). In the same way, links reading 'click here' only make sense in a mouse based environment.

Links like 'click here' also have problems with context in browsers that display a list of links.

Recommendations for making scripts accessible and making links accessible.

Example 6: Style-sheets

The stylesheets on this page give yellow text on a yellow background. All browsers with stylesheet support have an option to disable stylesheets, so any browser can use this page, provided the user realises that stylesheets are the problem.

In Netscape 4 especially, certain stylesheet properties can make the page unusable. Therefore, you must test carefully, and perhaps use CSS hiding methods to make sure browsers do not see harmful stylesheet properties.

Example 7: Colour combinations

If you use a background image, make sure that the real background is the same basic colour as it, as this will be used as a fallback. In this case, it is the background image that is the problem, and the fallback background colour is okay.

Any text-mode browser will have no problem here. Other browsers must either disable images, or you must try and find the link by waving the mouse about the screen... (if you are using a keyboard, then 'tabbing' to the link will be much more efficient).

The browser to use

To complete all seven stages without changing browser settings at all, then you need to use a recent version of Lynx (or a browser with similar capabilities and default settings). If you change browser settings, then the Opera 7 browser will also work for all except Stage 4. Mosaic 3 will work for all stages with some configuration changes

While the examples above were deliberately chosen to make a point, a similar set of examples could have been produced for any given browser. The importance of testing in multiple browsers and browser types cannot be understated.