In order to design accessible pages it is helpful to understand of how disabled
people use the Web. Information on how to fix these problems can be found
in the section "How to Create Accessible Pages".
Users with limited vision will increase or reduce the size of the font, depending on the nature of their eye condition. This can be achieved easily by changing the browser settings or using their own style sheet.
What can go wrong ?
If the font size has been set using an "absolute"
value such as pixel or point rather than a "relative"
size such as %, the text will not change size.
Some users will greatly magnify the size of text.
What can go wrong ?
If the page content has been placed within a table set to an absolute
width (eg 620 pixels) the text will be constrained to this width making it
harder for the user to read.
Users with no vision will turn off images and use a screen reader.
What can go wrong ?
• Screen readers can't access images unless they have an "alt"
(alternative text) tag to describe their content. This is vital if the image
is being used as a link. Text must be meaningful.
• Some screen readers only read the first 3 or 4 words of an "alt" tag and in extreme cases only 5 or 6 characters. If there are several alt tags on one line, it may cause a horizontal scroll bar to appear. As some screen readers only read text on the screen it is important that the page does not scroll sideways since content not shown on the screen will not be read out.
• The <Longdesc> tag, though not yet recognised by all browsers may allow a fuller description of an image if its content is significant. However, it can be hard to fully convey information displayed in an image in words which may be important for the user in an educational setting.
• Screen readers behave differently. You should expect them to read cell to cell, left to right, top to bottom. However some read line by line. Information contained within tables may not make sense so you need to plan carefully.
• Screen readers cannot access Flash and Shockwave elements. If these contain buttons users will not be able to navigate the site.
• Screen readers read all the text on the page. If the links menu is
at the top of each page, the user will have to listen to it every time a new
page is loaded.
Deaf people can't hear sound effects, audio and video clips - obviously.
What can go wrong?
Alternative forms such as transcripts or subtitles are not provided.
Dyslexic users will have their own colour and font style/size preferences. They will switch off the web page style sheet and replace it with their own. (see section on "Customising web pages").
What can go wrong ?
Style sheets built and used in a manner that prevents users from doing this
- avoid the use of deprecated HTML formatting tags especially <FONT>
Users unable to operate a mouse will use the tab and enter keys instead.
What can go wrong ?
Web pages using inacessible menu items such as drop down menus or pseudo links
(created using JavaScript) that require scrolling, or contain buttons built
into Flash or Shockwave elements that cannot be "tabbed".