Respectively, you might want to read: Learn HTML, Learn CSS, Learn JavaScript and Learn HTML DOM.
For reference, when I want to remember or search for some specific tag, I'm used to go to http://htmlhelp.com/reference/html40/ .
And I highly recommend you, when you're a little advanced in your learning, to periodically access Web Devout: http://www.webdevout.net/ . There you can find tables containing browser compatibility elements for HTML, CSS, JavaScript, DOM, articles, really interesting stuff.
Another awesome website I'm used to access, mostly for JavaScript clarifications and techniques: http://www.quirksmode.org/
I think these resources are 95% what I use when I need to figure out something regarding HTML/CSS/JavaScript/DOM and browsers compatibility.