The Tips - Mac Kung Fu - page 321

Open a Terminal window (open Finder, select the Applications list, and then
in the list of applications double-click Terminal within the UTILITIES folder), and
type the following:
DEFAULTS WRITE COM.APPLE.DOCK SHOWHIDDEN -BOOL TRUE;KILLALL DOCK
The changes will take effect immediately, so select an app and hide its program
windows by hitting COMMAND + H . The app's Dock icon will take on a ghostly
see-through look. To restore the app's windows, just click the Dock icon.
Reverting to Default
To revert to the default mode of hiding apps, open a Terminal window, and
type the following:
DEFAULTS DELETE COM.APPLE.DOCK SHOWHIDDEN;KILLALL DOCK
Tip 306
Cancel Drag and Drop Mid-Move
Ever found yourself changing your mind about dragging and dropping a file?
The problem is that if you let go of the file, it'll be moved or copied to wherever
your mouse is hovering over.
To cancel drag and drop, either hit ESC or drag the file to the menu bar at the
top of the screen and release.
Tip 307
Make Time Machine Forget a File
Time Machine periodically backs up every single file on your computer,
including personal data. That might include data you want to permanently
eradicate from your computer so it simply no longer exists—not as a file and
not within a backup. You can eradicate a file using Tip 6, Get Rid of Files—
Securely , on page 16 , but how do you remove it from all the Time Machine
backups that occurred since the file was created or copied to your computer?