Of course it's useful for cross-browser testing, but when I'm struggling with the CSS, I usually use the Web developers' toolbar, an addon for FireFox.
(Though I use Opera for my general browsing and website testing.)
Heh, well, I've never actually read anything about coding for mIRC outside of the mIRC help file, so I guess I use some quite odd methods of doing some stuff.. Didn't even know you could create functions in mIRC.
Anyways, thanks for the suggestions.