"Stoyan Stefanov is a Yahoo! web developer, Zend Certified Engineer, book author (""Object-Oriented JavaScript""), book contributor (""Even Faster Web Sites"", ""High-Performance JavaScript""), and technical reviewer (""JavaScript: the Good Parts"", ""PHP Mashups""). He speaks regularly about JavaScript, PHP, and other web development topics at conferences and his blog www.phpied.com. Stoyan is the creator of the smush.it image optimization tool and architect of Yahoo's performance optimization tool YSlow 2.0."