The Exceptional Performance team from Yahoo! developed a series of rules that determine how a website performs. YSlow gives web developers the opportunity to have their sites assessed based on 23 of those rules and suggests ways to improve the performance of sites that are not functioning optimally. It also provides additional information about sites, including summaries of their components, analyses of their performance, and offers even more tools that help to analyze he performance of sites.
The add-on is integrated with Firebug, a web development tool, which must be installed in order for YSlow to work. The full terms of the license agreement are available at http://wh.yslow.org/yslow-license, which is on the add-on’s official website, www.yslow.org.
Offers developers ways to improve the performance of their websites