How learn advance level in html

Answer 1

visit Tutorialspoint
w3schools
code academy
and try to practice code and also try to learn from others code 😉

Answer 2

https://developer.mozilla.org/

MDN (Mozilla Developer Network) is a great ressource to dive in for all stuff related to web... it's a little less tutorial oriented than W3School, but a little deeper technically accurate, without the hardness to read 'true' W3C (Worl Wide Web Consortium) official specifications ^^

MDN and W3School are both complementary root ressources for most of web developers ;)

Practice is the other side of skill improvement.
The better practice is the one motivate you for code something for your own use (or that will be used by someone important for you)... but if you stuck on getting ideas to code, you can usefuly help people here or over internet to debug/improve their codes, join other projects development on platform as Github, or even go play practice on site such as https://codewars.com (really good for practicing with leveled growing skills)...