Without knowing what it was doing and a way to consistently
reproduce it, I don't have a suggestion for you. Certain sites are
just going to require a lot of CPU and memory and there's not much
you can do about that. TenFourFox uses more memory than Safari
that code, and it has more aggressive caching in any case.
For the record, this is being typed on a 1GHz iMac G4. Right now
as I type, it shows about 25% CPU usage (it goes to about 8% when