No, I am specifically thinking of the “Net” displays of FireBug, which is of course the debugging plug-in for FireFox.

Other browsers offer similar developer-oriented debugging features.

I have more than one flat-spot on my head (“Doh!!”) from things that Firebug has told me about what an application was actually sending.   These sorts of problems are usually fairly effortless to resolve once you can see them, but, “aye, there’s the rub.”