Undo

  Choose Undo to cancel the most recent edit.  You can cancel
  only a single edit by choosing Undo.

  Choose Undo...  to cancel a series of edits.

  The Notepad editor defines a single edit as all keystrokes
  entered since the last time you either pressed the Delete key
  or repositioned the cursor by moving the pointer and pressing
  MB1.

  Additional topics:

  *   Redo

  *   Undo...

  *   Cut

  *   Copy

  *   Paste

  *   Clear

  *   Select All