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A group of users that is often overlooked are the visually impaired
users. By visually impaired we not only mean blind users but also
users who are long-sighted or suffer from some form of
colour-blindness. Although it doesn’t take a lot of effort to make
a site easy to use for most of these users, many sites don’t seem
willing to make that effort.
Basics
Although text that is hard to read is detrimental to the
user-friendliness of a site, many webmasters still don't take too
many pains when it comes to the legibility of their site. People
read 20 to 30% slower on a computer screen than they do on paper so
making reading even more difficult, isn't a good idea. The use of a
clear, sans-serif font and a reasonable font size (Verdana 10 for
example) and a pale, preferably white background and black letters
are minimum requirements, even for users who aren't visually
impaired.
Long-sighted
Use a relative font size instead of an absolute one
so users with visual disabilities can adapt it to their liking via
the option ‘View’ of the browser. For users with good eyesight
this doesn’t make any difference but for visually impaired users
it means a world of difference.
Clarity and legibility are important
for all aspects of a site, but that goes double for the navigation.
Text in images is harder to read than text in html and should be
avoided, even in the navigation. Another important downside of
navigation in image files or Flash is that the font size of the text
can't be adapted, which constitutes an extra obstacle for users with
a visual handicap. As a rule of thumb, always place text in html
where possible.
Style sheets allow you to define the look of a site
in a single document, which has a positive effect on the consistency
of the site. Some users who are long-sighted sometimes disable the
style sheet of a site and replace it by their own style sheet, in
which they push larger font types or more legible colours. To
accommodate these users, it is best to keep your style sheet as
simple as possible so your site is still legible without it.
Colour-blindness
Most people think colour-blind users are only a
negligible minority. Don't be fooled though, as much as 8% of white
males suffer from some form of colour-blindness, of which red-green
colour vision deficiency is the most common. Make sure colour-blind
users can use your website and avoid the use of the colours red,
green, brown, grey and purple right next to or on top of one
another. Also avoid any combination of these colours to indicate the
difference between a link that hasn't been visited and a visited
link. Remember to always underline links. Both users with and
without visual disabilities scan a web page rather than read it and
words that are underlined stand out more than words that are just in
a different colour.
Els Aerts & Karl Gilis
A more in depth version of this article
has appeared in
Tips & Advies Online Ondernemen, year 5, number 18 (Belgium and
the Netherlands).
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