This presentation was given at the 2009 AJAX Experience Conference by Gomez's CTO Imad Mouline and Director, Agent Technology. Today’s browser diversity brings new challenges to Web designers and developers. JavaScript loads and performs differently across browsers such as Internet Explorer 7 and 8, Firefox, Safari and Chrome, and can lead to inconsistent content rendering, poor Web performance, and frustrated end-users. Traditional methods for Web performance testing and monitoring cannot find and diagnose browser-specific, client-side performance problems. This session was designed to help developers learn how to: • Improve content rendering across multiple browsers and operating systems • Understand and improve object load order, browser by browser • Ensure that third-party content doesn’t degrade client-side performance • Realistically preview performance under load in each browser.