[haylem]

My reaction to this was "Oh hello Firebug, old friend" :)

It's not firebug, but it was nice that firebug at the time was installable as an extension or a simple bookmarklet, for just about any page, before "Dev Tools" became integral parts of our modern browsers.

EDIT: Firebug's old page is actually still up with a bit of history: https://getfirebug.com/index.html