A free 12 chapter book on the open source Mozilla browser, which is also a framework for building cross-platform applications using standards such as CSS (Cascading Style Sheets), XML languages such as XUL (XML-based User-interface Language), XBL (eXtensible Binding Language), and RDF (Resource Description Framework), etc.
http://books.mozdev.org/chapters/index.html
Enjoy!
Creating Applications with Mozilla
