If you find the prospect of wading through the w3c specs daunting, and you are a lucky user of Mozilla or Opera, you’ll find these sidebar tabs invaluable. Yes, follow that link even if you don’t know what a sidebar tab is. I didn’t either before I went there.
These tabs conveniently list all the HTML and CSS elements in your sidebar. Click on the tag, attribute or element you need information on, and you’ll be transported to the relevant place in the w3c specifications. Without the trouble of finding the right spec, and then the right place in the spec. Still there?
I can’t imagine I discovered about them only now.