Firefox

You should be able to download the old version from here:

http://www.macupdate.com/app/mac/10700/firefox

You can download 3.6.16 which is the current version that will run on PowerPC's from http://www.mozilla.com/en-US/firefox/all-older.html

This was ****-poor conduct by Mozilla. There was no read-me w/ the 4.0 update noting that the sys reqs had changed.

For those who have not deleted their older 3.6.15 or before, and want 3.6.16,
you can choose to 'check for updates' within Firefox' Help in the main menubar.

This will check for and update the browser to the last 3.6.x version available.

Since I have both Mac OS X 10.4.11 and OS X 10.5.8 on PPC-based Macs,
and both are running Firefox 3.6.16, I have not tested the Leopard system's
ability to use the later (and recently released from beta) Firefox 4.x. series.
And would certainly read around, before committing PPC Macs to a mistake.

The discussion of non-support for Tiger 10.4.11 in Firefox browsers after 3.6.x
had been online for a time, before these latest moments of recent discovery.

Not sure of the options open to older Mac OS X 10.4.11 users, after 3.6.x;
except to hope Mozilla keeps the Camino browser updated awhile longer.
And maybe Opera will keep something available; perhaps iCab (for a fee.)

The other issue is the lack of Flash and Shockwave support for Tiger 10.4.11
& diminished support for PPCs in general, as Leopard 10.5.8 gets left behind.

Good luck & happy computing! 🙂

Since I have both Mac OS X 10.4.11 and OS X 10.5.8 on PPC-based Macs,
and both are running Firefox 3.6.16, I have not tested the Leopard system's
ability to use the later (and recently released from beta) Firefox 4.x. series.

Firefox 4.0 is only for Intel-based systems. Don't know if there are any plans for PPC support or not.

"There was no read-me w/ the 4.0 update noting that the sys reqs had changed."

Actually, it's on FF website.

I'm running the latest Firefox 4.0 on 10.5.8 PPC G4/G5 thanks to MonkeyBoy...

http://x704.net/bbs/viewtopic.php?f=17&t=5211&p=62869&hilit=monkeyfox#p62869

Then there's TenFourFox for 10.4.11...

http://www.floodgap.com/software/tenfourfox/

http://discussions.apple.com/thread.jspa?messageID=13151846

Nope, but it supposedly has many Security fixes.

MonkeyBoy's CPU optimized versions do result in lower CPU usage, especially if you Hide FF or send it to the back.

If there may be some continuing support for the TenFourFox or MonkeyBuddy fix,
those could be a way to go, at least for a time, with PPC G4/G5 and Tiger/Leopard.

{Though it seems a little odd but not too strange that the Firefox update site offers
their new Firefox 4.0 release, blindly to all visitors; that can be a problem for some.
In the same vain, Flash components for vintage Mac OS are difficult to navigate.}

Oh well. If it weren't Fun, it'd be too Serious...
Good luck & happy computing! 🙂