OStatic

If you're a Web developer, it's a pretty good bet that one of your most important tools is Firebug, an open-source debugger for HTML, CSS, JavaScript, and Ajax that works inside of the open-source Firefox Web browser. Since it was first unveiled several years ago, Firebug has taken the Web-development world by storm, revolutionizing developers' ability to modify, test, and debug Web applications. In the last month, Firebug has received hosting and development assistance from Mozilla, a change that will almost certainly benefit both the software and the community.