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