A few days ago I posted about Firebug, the Swiss Army Knife of the developers' plugins. Last week Yahoo released an add-on for Firebug: YSlow. YSlow measures web page performance based on the best practices evangelized by Yahoo!'s Exceptional Performance team. Since many of these best practices focus on the frontend, YSlow is integrated with Joe Hewitt's Firebug, the web development tool of choice for frontend developers. After checking your site against the 13 rules of High Performance Web Sites, it rates the performances of your site with an A to F grade. I run the tool on a...