HTML, CSS and Javascript

Personally I use Strict DOCTYPE as it render more consistently between platform.

To simplify javascript work I use jQuery which is a lightweight framework that let you quickly manipulate the DOM and deal with events in a manner where you don't have to concern yourself much about differences between the platforms.

For in introduction to HTML and CSS I recommend HTML Dog. It's up to date and will recommend best practices. htmldog.com

For lookup references to most web related languages: www.w3schools.com

The ultimate reference to web standards: www.w3.org