Accessibility is the practice of making your multimedia content accessible to all learners, regardless of their abilities, disabilities, or preferences. Accessibility can improve the usability, inclusivity, and compliance of your online lectures. To make your multimedia content accessible, you should follow the Web Content Accessibility Guidelines (WCAG), which provide standards and recommendations for web design and development. For example, you should provide captions, transcripts, and audio descriptions for your videos and audio, use alt text and descriptive text for your images and animations, and ensure that your interactive elements are keyboard and screen reader friendly.