Why You Should Care About Web Form Usability
Many organizations don’t publish any email addresses on their website because of email spam. On those sites, a contact form is the only way for a visitor to reach the site owner. This should imply that website designers take a lot of care to ensure that web forms are usable by anyone, as email is.
The accessibility issues associated with CAPTCHAs for visually impaired people are well known, so I’m not going to discuss this further. I’m going to talk here about people fortunate enough to have normal sight and hearing, but who may also have a hard time using web forms.
Many CAPTCHAs systems are difficult to read because they were designed to defeat automated attempts to read the image using OCR. As the designer of a CAPTCHA system, I’ve been trained more than the average web user to reading them. Still, I’m surprised by how often I miss the correct code on the first try. A high level of image obfuscation may be needed for very large websites like Google or Yahoo, for which it is realistic to believe some people would be ready to invest a lot of effort to break the system, given the potential payoff. But it’s very unlikely someone will try to break the CAPTCHA of the average website. So those should at least be easy-to-read and short, if CAPTCHA there has to be.
Not every web user downloads images. More and more people browse the web via cellphones, on which web usage is charged per megabyte. Users are then inclined not to load images to reduce costs. This is even the default setting on some low-end cellphones. Those users won’t see the CAPTCHA.
Audio CAPTCHAs are commonly accepted as a good complement to visual CAPTCHAs for the visually impaired. Besides the technical reasons for not being able to listen to an audio file on a computer (e.g. no sound support, no loudspeakers or earphones fitted), there are also social reasons. First, there are social environments where it may be rude or prohibited. For example in public libraries and open space offices. Second, the web is global and non-native English speakers may not be able to understand what is said in the audio CAPTCHA.
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