By law, all websites owned by the US federal government must comply with the Section 508 Federal Accessibility Standards. For private sites, such compliance may not be legally required, but it’s still a good idea; adhering to standards ensures that all of your potential customers can utilize your site.
The main component in designing an accessible website is ensuring that any non-text element, be it photos, music, video, etc, has a text equivalent; this can mean adding descriptive text to a photo or subtitles to a movie. Some of the most common disabilities include:
Ensure that any audio that is required to fully use the site has accompanying text; for example, you can add captions to a video using software like Camtasia, and provide transcripts of podcasts. In many cases, audio-to-text programs like Dragon NaturallySpeaking can do much of the work for you.
Designing for vision loss often means desiging for screen readers, which has the side benefit of making your website easier for spiders as well. Ensure that alt tags contain useful information, and consider that blind users may not be able to tell if part of the screen updates without a page reload. People using screen readers may also appreciate being able to skip repetitive navigation links, rather than having to wait for the entire menu to be read out every time. Finally, ensure that all elements are accessible using the keyboard only.
A significant percentage of the population has difficulty discriminating colors; avoid using color as the only way of transmitting important information, and choose high-contrast color combinations. There are tools available that allow you to view your website as it would be seen by people with various types of colorblindness; you can also read more about optimal color choices here.
When adding movie captions, etc, be sure that related information is synchronized; captions become annoying rather than helpful if they show up too late! CSS is a great thing for designing accessible websites, as it encourages thinking about content separately from style; be sure that it’s possible to read the page and have it make sense without loading the associated stylesheets.
Ensuring that your website is accessible can be a pain at first, but your customers will appreciate it. It’s always worth a little extra effort to have your site read by the widest possible audience!