Possible Duplicate:
Switch between windows on Mac OS X?
In Windows, you switch between active windows with Alt-Tab. This behavior includes all running apps and all instances of each app. So if you have Calc open and 3 instances of Excel, there are 4 items to switch through.
In OS X, Command-Tab switches between apps but does not include multiple instances of each app - only the active instance. So if you have Calc open and 3 instances of Excel, there are 2 items to switch through. Command-` is used to switch between multiple instances of an app.
Can OS X's Command-Tab behavior be changed to work like Alt-Tab does in Windows?