The title of the book (domain name of the site) is the subject the book (site) is about.
Each chapter (doorway page) contains a keyword or phrase.
Each chapter has information containing that keyword or phrase.
The book (website) must have quality content: people must have a need or want to be there, and see an overall idea (theme) which is permeated throughout.
The language must be simple enough for people to grasp. (clean, uncluttered code)
Each external link into the website is like a critic raving about the book and recommending it to others.
Page numbers, and chapter numbers are like the internal linking system of the website: without them, the end user is lost.
The site map of the website is like the index at the back of the book, giving information on how to get to any topic quickly.
Each keyword or phrase expands into a chapter (doorway page) and each chapter supports or builds the main topic of the book (website).
More than one domain, is like a series of books, each supporting the other.
