The last few years have seen a bevy of case studies from Google, Yahoo!, AOL, Microsoft, Mozilla, Shopzilla, Netflix, and others testifying that making web sites faster drives traffic to the site, improves the user experience, increases revenue, and reduces operating costs. The VC community has caught on and are backing a number of web performance startups. All of this has culminated in the emergence of a new industry: Web Performance Optimization (WPO). Join Steve Souders as he recounts the evolution of WPO and lays out the biggest challenge for creating faster web sites: JavaScript.