Web Accessibility: "Is justified text, err... justified?"

Have had a few people - most recently JackP on Accessify Forum - asking about the reasoning behind the general recommendation that designers avoid the use of justified text on web pages, so I thought I'd post a few useful references here - feel free to chip in with any other useful links to info about why justified text isn't regarded as a Good Thing on the web.

There are two main reasons for justified text not working well on web pages - the way we actually read text when we're viewing it on screen, and the way browsers handle text justification.

Text is more difficult to read on screen than it is in hard print because of differences in resolution, and the fact that, even if we're not consciously aware of it, the image on screen is not totally static (the image is constantly being refreshed, many times a second). So anything which makes it more difficult to find and read words, phrases, paragraphs, etc, is generally not a good idea.

Browsers are not very good at handling justification and displaying justified text, and one is likely to be presented with text where the spaces between words varies a lot, unlike the more subtle variation in spacing that is achieved in printed text. This extreme variation in the spacing makes the text more difficult to read - instead of the eye being able to move smoothly along the line of text, it has to move in "fits and starts", searching for and jumping to the start of each word.

While someone with no sight problems or reading difficulties might find this no more than a mild aggravation, it can present real problems to anyone using screen magnification software (since the gaps between words are also magnified), and to people with conditions such as dyslexia. Some people with reading difficulties and/or some cognitive disabilities find that the "rivers" of white space which can easily occur within justified passages of text on screen form a more distinct pattern than the actual words themselves, making the text extremely difficult to read and comprehend.

Some links to articles/info about or related to this:

• An Accessibility Frontier: Cognitive disabilities and learning difficulties (Usability.com.au)
• Developing sites for users with Cognitive disabilities and learning difficulties (Juicy Studio; a simplified version of the "An Accessibility Frontier" article listed above).
• Web Accessibility for Dyslexia (University of Manchester)
• Designing web pages for dyslexic readers (Dyslexia Online Magazine for Parents)

Technorati subject tags: Accessibility, Web Accessibility, Web Standards