Achieving Web Accessibility can be a very difficult task. New laws state that companies need to make their services and products accessible all users, regardless of any disability, and this requires extra attention when designing a website. Unfortunately, this has led many less-vigilant designers to offer solutions that are only half-measures in Web Accessibility.
You may have seen a display that looks a bit like this on a website that you've visited:
Text Size: A A A
This feature is designed to make the website more accessible to people with a visual impairment, such as short-sightedness. Most web browsers have the ability to configure the default text size to a size that the user is comfortable with, so why is offering three font settings of any benefit to the designer?
The simple answer is: many designers control the size of the font and overrule the browser settings so that the text fits nicely into the spaces they've provided. This means that, regardless of the preferences stated by the user, the designer has decided the size of the font that will be displayed. When designers use the "three font setting" approach, they're inter-changing specific sizes, which only gives the user partial control over the font size.
The solution is simple, really. Designers can specify font sizes as relative rather than specific values (i.e.; instead of stating font size as a value such as "16pt" or "30px", they can use "medium" or "80%"). The relative values draw through the user default and displays font sizes based on that value.
There's really no excuse for not doing it.
Unfortunately, too many organisations have been convinced that the "three font setting" approach is adequate to ensure accessibility when, in fact, it's a warning sign that the site offers a half-measure in accessibility for one particular disability group (visual impairment) when the requirements of full accessibility are far more extensive.