Over at Macworld, Lex Friedman explains how to turn on and use two-factor authentication with a Google account to combine a fixed password with a constantly updated additional code sent as a text message or accessible from a smartphone app. Be aware that two-factor authentication may be more trouble than it’s worth, depending on how often you need to sign into your Google account. follow link
Enter Dashboard, Expose, or Spaces Temporarily
Hold down F9, F10, F11, or F12 (or whatever you've set for the Expose and Spaces keyboard shortcuts) for a few seconds, and then release the key to enter and leave the appropriate mode without having to press the key again. This is particularly useful for Dashboard, in which you can check the contents of a widget and then return to your work with only a single key press.
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Enable Google’s Two-Factor Login