W3Cx: Introduction to Web Accessibility is an introductory course from the World Wide Web Consortium (W3C) that covers the foundations of creating accessible web content and applications. I am one of the course trainers for the development section.
Course overview
The course introduces the principles, standards, and practical considerations that help make the web usable by people with disabilities. The development section focuses on applying accessibility requirements throughout the implementation process.
Based on W3C WAI's foundations course information, the curriculum covers accessibility principles, disability and assistive technology context, standards and conformance, planning and design considerations, authoring and development practices, and evaluation and testing approaches teams can apply in day-to-day product work.