W3Schools:
link: https://www.w3schools.com/

W3Schools.com is a popular website to learn web technologies. It contains tutorials related to HTML, CSS, JavaScript, JSON, PHP, Python, AngularJS, SQL, Bootstrap, Node.js, jQuery, XQuery, AJAX, and XML.

TutorialsPoint:
link: https://www.tutorialspoint.com/

TutorialsPoint is an online tutorials library having a collection of tutorials on various technical and non technical subjects. It contain tutorials on almost all web technologies. But these tutorials are mostly for beginner and intermediate level.

Some usefull youtube channels for web development:

TheNewBoston
https://www.youtube.com/user/thenewboston/playlists

John Morris
https://www.youtube.com/user/JohnMorrisVideo/playlists

Programming with Mosh
https://www.youtube.com/user/programmingwithmosh/playlists

HowCode
https://www.youtube.com/user/CreatiiveCode/playlists

Udacity:
https://udacity.com

Html Css Free Couce on udacity
https://www.udacity.com/course/intro-to-html-and-css--ud001

Coursera:
https://www.coursera.org/

Some Coursera Cources:

https://www.coursera.org/learn/html-css-javascript-for-web-developers

https://www.coursera.org/learn/web-development

https://www.coursera.org/learn/bootstrap-4

https://www.coursera.org/learn/responsive-web-design#

Some Paid Resouces are:

Udemy
https://www.udemy.com/

Lynda
https://www.lynda.com/