In the deep dark past of the web, many programmers learnt about how to code HTML, CSS and Javascript by a mixture of books, other developers and hacking apart existing web code. This lead to some very messy outcomes with cut and paste solutions that allowed bad code to live on. Web development is now a mature profession, and has an abundance of quality resources available. For a new front end web developer the Opera Web Standards Curriculum is one of the best resources.
The site is a fantastic collection of 37 articles and counting that lead from a general web introduction through HTML, accessibility and CSS. There are great articles on colour theory and web typography. The site is aimed at students and educators in the hope they will teach their students the right way to do things on the web.
The W3C may publish the standards but the Opera Web Standards Curriculum is a great practical resource to learn them.