Michael Urman is not a lawyer, and thus is going to try to put this in plain speech. If you're not sure if he's allowing you to do something with his works, ask before you do it.
That said, all the basics implied by publishing on the web are true: you're free to download it in your browser so you can read it. If you get ideas from his pages, including his stylesheet, feel free to use them. He'd prefer you not copy anything more than a paragraph or a CSS selector verbatim without somehow crediting him.
Thanks!