When designing your website it is important to make your web design user friendly as this will help people find their way to important information on the site and lead to conversions. It is also important that your website is accessible to all, this is a legal requirement as well as could lead to more visits and sales.
A lot of usability issues can be addressed at the design stage prior to development. Having an amazing website is pointless if it’s too complicated or creates barriers for users to access content
Usability: Use a standardised layout, consider user familiarity, search functionality, sitemaps
Browsers: Does it render properly in IE7+, Firefox 3+
Analytics: High exit rate on certain page, is there content on the site that is never viewed?
Discrimination act; In 2000, an Australian blind man won a court case against the Sydney Organizing Committee of the Olympic Games (SOCOG). This was the first successful case under Disability Discrimination Act 1992 because SOCOG had failed to make their official website, Sydney Olympic Games, adequately accessible to blind users.
Most websites that follow best practice development techniques are considered accessible; they will be readable by screen readers, search engine robots etc.
Additional options can be provided such as the ability to adjust the text size and adding keyboard controls etc; however most browsers provide this functionality.
Automated programs and tools can give your site an approximate rating; getting a AA standard is very challenging!