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FF 4.0 download says "not compatible" w/my system. (iMac pwr pc G5) What's going on? Do I need to revert back to FF 3.xxx. If so, where do I find old FF browser?

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Downloaded & installed FF 4.0 on iMac Power PC G5 (2Ghz - 1.5 GB RAM). When opening new FF, error message states "not compatible with this system". Had been running older 3.xx.xx with no problems. (Just wanted to upgrade to the 'latest & greatest'. I have loaded 4.0 onto my MacBook w/intel processor - no problems. Is 4.0 not backwards compatible with pre-intel processors?

Downloaded & installed FF 4.0 on iMac Power PC G5 (2Ghz - 1.5 GB RAM). When opening new FF, error message states "not compatible with this system". Had been running older 3.xx.xx with no problems. (Just wanted to upgrade to the 'latest & greatest'. I have loaded 4.0 onto my MacBook w/intel processor - no problems. Is 4.0 not backwards compatible with pre-intel processors?

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Firefox 4 requires at least OS X 10.5 and an Intel Mac. There is a third party version of Firefox 4 that runs on OS X 10.4/10.5 and PPC Macs, for details see http://www.floodgap.com/software/tenfourfox

If you prefer, you can get the latest version of Firefox 3.6 from http://www.mozilla.com/en-US/firefox/all-older.html