Principles of website accessibility testing
The first principle in accessibility testing is to look at the design itself. Is the interface logically designed and easy to understand? The screen should not be cluttered and there should be no navigational inconsistencies. Also, links should be descriptive and compatible with screen readers. In fact, navigation is one of the most important aspects of accessibility. All users should be able to navigate easily through the site and this includes keyboard navigation.
Text is another important part of accessibility. It should be clear and easy to read, as confusing fonts can be major obstacles to visually impaired users. User accessibility testers should ensure that letters are clear and text blocks a readable. According to W3C, the minimum contrast ratio between text and background should be 4.5:1 for normal text and can go as low as 3:1 for bold or large fonts. The spaces between lines should be no less than 25% the size of the font and minimum font size should be no less than 16 pixels.
HTML should be optimized for screen readers. This means that navigation menus should be at the bottom of the page which, unfortunately, is the least workable place to put it for sighted readers. Fortunately, cascading style sheets have solved this problem.
Also, avoid color coding. While using color codes can be a fast way to communicate, it must be remembered that not everyone can see every color and some people see the same colors in different ways. For example, some people confuse red and green or brown and green while a very small percentage are totally color blind and see the world only in black and white.
Empathy is the basic principle for building and testing accessible web sites and applications. Builders and testers must put themselves in the other fellow's shoes. That may require a bit of research concerning what problems have been addressed in the past, and an understanding of W3C guidelines. It comes down to ensuring that everyone has equal access.