iBook Clamshell 366mhz. I don't see a reason why it wouldn't work if it works with something so old, did you use the pre-release 1.0 or the original 1.0. I'm pretty sure that the pre-release didn't work.
I myself am running 10.1.5 on my machine, i currently use Firefox 1.0, its still a little slow but it is a whole lot better than IE 5.
Try this site:
mac.oldapps.com/firefox.php