Book excerpt: Do you have an idea for a Facebook application? With FBML Essentials, you'll learn how to build it quickly using the Facebook Markup Language (FBML) and other easy-to-use tools in the site's framework. If you can develop a website with HTML, writing a Facebook application with the help of this book will be a breeze. Of course, Facebook is not just another website. Any applications you write for it will have a potential audience of 16 million dedicated users. It's not just another social networking site, either. Under the surface, Facebook is pretty sophisticated, with a development toolkit that includes it's own modified version of HTML -- FBML -- to customize the look and feel of your Facebook applications. With FBML Essentials, you not only learn how to get started with this toolkit, you also get a complete reference on every FBML tag Facebook has ever written, with examples of how each tag works and advice on the best ways to use these tags in your code. This book includes: A walkthrough of a sample Facebook application Design rules for using images, CSS, JavaScript, and forms Specific chapters on tags -- authorization tags, logic tags, user/group tags, profile-specific tags, and more Messaging and alerts using FBML Creating forms with FBML Facebook navigation Notifications and requests Dynamic FBML attributes, including MockAJAX How to test your FBML code A chapter on FBJS, Facebook's version of JavaScript If you want to try your hand at writing a Facebook application, you have a willing audience, an easy-to-use toolkit, and the perfect guide to get you started. FBML Essentials will help you take your idea from conception to working application in no time.