If your like me and sometimes need to debug js in different browsers for web development. Sometimes its helpful to use debugging tools available with different browsers. Mozilla has the really useful firebug tool, which I use all the time and which is easily installed via mozillas browser plug in environment.
Safari on the other hand is a little trickier, I stumbled accross this today which certainly helped me.
Open up a terminal window on your mac and run this command
defaults write com.apple.Safari IncludeDebugMenu 1
Quit Safari and reopen, you should now see a 'Develop' tab along the top of your mac toolbar (where preferences is).
You can use this to do all sorts of useful profiling of your scripts on safari, which I have found most useful.