Restore previous Safari version from .SafariArchive.tar.gz
Did that new Safari update (5.1) break something and you'd like the old version back? Thanks to Apple's prescient yet secretive engineers, there's a way.
When Safari does an upgrade it saves the previous version in this location:
/Library/Application Support/Apple/.SafariArchive.tar.gz
To restore Safari, have tar to expand the archive to the root folder:
sudo tar -xvf /Library/Application\ Support/Apple/.SafariArchive.tar.gz -C /
sudo rm -rf /private/var/db/receipts/com.apple.pkg.Safari51SnowLeopard.*
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