Stoyan Stefanov has worked for Yahoo!, SAP Canada, and currently Facebook. He's the creator of Smush.it image optimizer and the performance tool YSlow 2.0. He's PHP Zend-certified, author of "JavaScript Patterns", "Object-Oriented JavaScript", contributor to "High-Performance JavaScript" and "Even Faster Web Sites", PHPAdvent.org and a conference speaker (JSConf, Fronteers, Ajax Experience, Velocity, PHP Québec)