Firebug, or the lack there of, WAS the only thing stopping me from using Firefox 3 on a more permanent basis, especially now it’s much faster and integrates better on the Mac and given that Safari seems to be quite selective at what it caches. But not anymore.
With Firebug being such a great tool, I [...]

First, some clarification. YSlow is a pluggin for Firebug, not Firefox. It’s installed as a Firefox pluggin, but it actually enhances Firebug. Accordingly it requires Firebug to be installed.
YSlow adds a new YSlow tab to Firebug and in this tab it rates your page on the scale A to F, based on [...]