I tried navigating to the http://thehtml5herald.com/ site mentioned in the HTML5 book and I keep receiving an internal server error. Are the authors of the book planning to make that site functional again?
I am guessing (the unexpected temporary downtime) will most likely be due to the new upgrades they are making at SitePoint it looks like they haven't got things sorted yet. You'll probably have to ask the forum administrator or something? I am a only SPF volunteer and don't work for SP.
If you can access the book's code archive, I believe an off-line version of the 'Herald' site is also available.