I'm posting this in the CSS forum in case anyone here can find a solution to be put forward to the book author.
Page 132 of the book is where the Rich Tooltips example can be found, and page 138 is where we're told to apply a CSS fix for Safari and Opera.
// Fix for Safari2/Opera9 repaint issue
document.documentElement.style.position = "relative";
The problem, is that when using Firefox in situations where you have scrolled down the page, setting this position to relative forces the web browser to scroll to the top of the page, and you lose the fancy tooltip.
While it's possible to fix this problem using browser sniffing, it's better if that sort of technique was not required.