From the Mozilla Developer Network, a checklist for the accessibility of your designs:
- Make sure your HTML is as semantically correct as possible. Validating it is a good start, as is using an Auditing tool.
- Check that your content makes sense when the CSS is turned off.
- Make sure your functionality is keyboard accessible. Test using Tab, Return/Enter, etc.
- Make sure your non-text content has text alternatives. an Auditing tool is good for catching such problems.
- Make sure your site’s color contrast is acceptable, using a suitable checking tool. [ Here’s a good one. ]
- Make sure hidden content is visible by screenreaders.
- Use ARIA to improve accessibility where appropriate.
- Run your site through an Auditing tool.
- Test it with a screenreader.
- Include an accessibility policy/statement somewhere findable on your site to say what you did.
The WebAim WAVE (web accessibility evaluation) tool is an eye-opening experience. At the WAVE web page, you enter a URL, and the tool generates a visual report on the accessibility barriers in your site.