Beginner
Learn HTML (www.codecademy.com)
HTML Best Practices (github.com)
HTML Beginner Tutorial (htmldog.com)
How to Use the HTML5 Sectioning Elements (blog.teamtreehouse.com)
Learn HTML in 12 Minutes (www.youtube.com)
HTML Content (www.codecademy.com)
Marksheet (marksheet.io)
w3schools (www.w3schools.com)
Organizing HTML & CSS (www.codecademy.com)
Front End Interview Handbook (github.com)
HTML Fundamentals (www.codecademy.com)
Intermediate
HTML Intermediate Tutorial (htmldog.com)
Advanced
HTML Advanced Tutorial (htmldog.com)