<ul>
	<li><a href="intro">Introduction to Understanding WCAG 2.1</a></li>
	<li><a href="understanding-techniques">Understanding Techniques for WCAG Success Criteria</a></li>
	<li>Perceivable 
		<ul>
			<li><a href="text-alternatives">Text Alternatives</a>
				<ul>
					<li><a href="non-text-content">Non-text Content</a></li>
				</ul>
			</li>
			<li><a href="time-based-media">Time-based Media</a>
				<ul>
					<li><a href="audio-only-and-video-only-prerecorded">Audio-only and Video-only (Prerecorded)</a></