HTML best practices
https://www.webfx.com/blog/web-design/20-html-best-practices-you-should-follow/

https://www.linkedin.com/learning/html-essential-training-2017/next-steps?autoAdvance=true&autoSkip=true&autoplay=true&resume=false


http://html5doctor.com

Additional resources
http://www.w3.org/TR/html5
 
http://www.w3.org/TR/html5-diff

http://validator.w3.org
 
https://developer.mozilla.org/en-US/

http://www.webplatform.org

https://www.html5rocks.com/en/

https://www.html5rocks.com/en/tutorials/

https://developers.google.com/web