About a month ago, a coworker told me about FireBug. I did not get around to installing it myself until yesterday. Boy, I should have listened to him a month ago.
In the author’s own words:
FireBug lets you explore the far corners of the DOM by keyboard or mouse. All of the tools you need to poke, prod, and monitor your JavaScript, CSS, HTML and Ajax are brought together into one seamless experience, including a debugger, an error console, command line, and a variety of fun inspectors.
Bottom line, too cool and too useful to describe. You just have to try it yourself. My favorite feature (Because I am completely innept at HTML) is the “Inspector” tab. With that tab open, you can move your mouse around an open web page, and it will highlight the source code to whatever object you are hovering over.
Posted by wulimaster 
WuLi's Waste Of Bandwidth 