For example, while developing I like to add in timers to PHP based pages to show how long things are taking. This way if a SQL statement needs some fine-tuning or a change slows things down I can see it happen. FireBug extends this to the entire page and the HTTP traffic. Here’s what happens when I load a page that has a few JavaScript calls, small images and a single CSS link in it,

Straight away it’s obvious what’s taking up the bulk of the time – those two library calls. Once I take those out of the equation the load time drops to under a second. And through all this the PHP timer function only shows me how long the server-side work is taking.

With FireBug I know who (in a geeky code way) is doing what and with who and I can act on it. Now that’s helpful.