If you have an older, slower Mac and have updated to Flash Player 10, you may have experienced some degradation of web browser performance after the update. You might be able to get some of that performance back by downgrading to version 9. Adobe wants you to use version 10 in Mac OS X 10.4 or higher, but version 9 is just as good. What's more, version 9 has kept up with all the security updates, so you'll be no less safe using it.
Go to http://get.adobe.com/flashplayer/otherversions/
and select 'Macintosh OS X 10.1 - 10.3' from the popup menu. You can then proceed to download Flash Player 9.
You'll be downloading 'install_flash_player_9.dmg'. When the download completes, double-click the image file; a volume will be mounted and a window will open that looks something like this: