It's hosted on Opera Software's very nice developer site, but applicable to most "modern" browsers:

1: Introduction to The Web Standards Curriculum/Table of Contents @ Opera Developer Community.

It's not encyclopedic like W3Schools Online Web Tutorials but is meant to encourage good practices.

Of course, let's not forget the other big browser guys, in alphabetical order:

Web Page Development: Best Practices @ Apple Developer Connection (top level: Internet & Web @ Apple Developer Connection) (heavy MacOS platform pitch)

Internet Explorer Developer Center @ Microsoft Developer Network and Web Development Library @ MSDN (hard to find general training that isn't specific to a MS development tool)

Web Development @ Mozilla Developer Center (top level: Main Page @ MDC) (some material is quite dated)

Apologies for omitting your favorite, if I omitted it.