I have discovered a nice little development by . it's an extension of his TenFourFox PPC Mac modernised Firefox-forked web browser, in this case known as TenFourFoxBox. It enables the creation of site-specific browsers, or web browsers that direct all their resources to a single website.
I was unable to get it to work with Cappuccino, but it's OK on admin.10C, go figure.
I'm using it on the 2005 12-inch G4 PowerBook, the one with the really nice keyboard.