Apple - What is a good web browser for OS X 10.4 Tiger?
TenFourFox gives you the current version of Firefox in builds optimized for G3, G4 and G5 PowerPC processors that runs on Mac OS 10.4 and 10.5.
You can try camino, which requires Mac OS X 10.4 or later. Just nice for you.
Their webpage says they are no longer supporting it though:
After a decade-long run, Camino is no longer being developed, and we encourage all users to upgrade to a more modern browser. Camino is increasingly lagging behind the fast pace of changes on the web, and more importantly it is not receiving security updates, making it increasingly unsafe to use.