The current trend of using software as a service has led to an increase in the development and use of Web (or hosted) applications. Also, more recently, the opportunities of rich Internet applications (Web 2.0 and otherwise) offer up new design issues and solutions. But despite the pervasiveness of Web Applications, there are no standards for their design--unlike the standards offered by Windows or Macintosh platforms, for instance. So there are limited restrictions on how interaction is designed. This results in a wide variety of appearance and behavior of applications--even within the applications created by the same company, even those that have documentation standards and look-and-feel guidelines. We need only to look at ourselves to see some of these broad issues. The solution is design patterns for web applications, similar in concept to the design patterns now available for web site design and software engineering. That is the focus of this book.