Nicholas C. Zakas is a front-end consultant who specializes in user interface design and implementation for web applications using JavaScript, Dynamic HTML, CSS, XML, and XSLT. Has has 15 years of web development experience and spent nearly five years at Yahoo! in various roles, including principal front end engineer for the Yahoo! homepage and contributor to the Yahoo! User Interface (YUI) library, having written the Cookie Utility, Profiler, and YUI Test.Nicholas is the author of Professional JavaScript for Web Developers and High Performance JavaScript, a co-author on Professional Ajax, and a contributor to Even Faster Web Sites. He has also written for several online sites such as WebReference, Sitepoint, the YUI Blog, A List Apart, and the Web Performance Advent Calendar.Nicholas regularly gives talks about web development, JavaScript, and best practices. He has given talks at companies such as Yahoo!, LinkedIn, Google, Netflix, TripAdvisor, and NASA, and conferences such as the Ajax Experience, the Rich Web Experience, OSCON, WebDirections, Fronteers, and Velocity.Through his writing and speaking, Nicholas seeks to teach others the valuable lessons he's learned while working on some of the most popular and demanding web applications in the world. He firmly believes that no difficult problem should need to be solved more than once.