Index: CKEditor/trunk/_source/plugins/about/plugin.js
===================================================================
--- CKEditor/trunk/_source/plugins/about/plugin.js	(revision 3607)
+++ CKEditor/trunk/_source/plugins/about/plugin.js	(revision 3608)
@@ -10,4 +10,5 @@
 		var command = editor.addCommand( 'about', new CKEDITOR.dialogCommand( 'about' ) );
 		command.modes = { wysiwyg:1, source:1 };
+		command.canUndo = false;
 
 		editor.ui.addButton( 'About',
Index: CKEditor/trunk/_source/plugins/clipboard/plugin.js
===================================================================
--- CKEditor/trunk/_source/plugins/clipboard/plugin.js	(revision 3607)
+++ CKEditor/trunk/_source/plugins/clipboard/plugin.js	(revision 3608)
@@ -61,4 +61,5 @@
 	{
 		this.type = type;
+		this.canUndo = ( this.type == 'cut' );		// We can't undo copy to clipboard.
 	};
 
Index: CKEditor/trunk/_source/plugins/find/plugin.js
===================================================================
--- CKEditor/trunk/_source/plugins/find/plugin.js	(revision 3607)
+++ CKEditor/trunk/_source/plugins/find/plugin.js	(revision 3608)
@@ -14,5 +14,6 @@
 				command : 'find'
 			});
-		editor.addCommand( 'find', new CKEDITOR.dialogCommand( 'find' ) );
+		var findCommand = editor.addCommand( 'find', new CKEDITOR.dialogCommand( 'find' ) );
+		findCommand.canUndo = false;
 
 		editor.ui.addButton( 'Replace',
@@ -21,5 +22,6 @@
 				command : 'replace'
 			});
-		editor.addCommand( 'replace', new CKEDITOR.dialogCommand( 'replace' ) );
+		var replaceCommand = editor.addCommand( 'replace', new CKEDITOR.dialogCommand( 'replace' ) );
+		replaceCommand.canUndo = false;
 
 		CKEDITOR.dialog.add( 'find',	this.path + 'dialogs/find.js' );
Index: CKEditor/trunk/_source/plugins/maximize/plugin.js
===================================================================
--- CKEditor/trunk/_source/plugins/maximize/plugin.js	(revision 3607)
+++ CKEditor/trunk/_source/plugins/maximize/plugin.js	(revision 3608)
@@ -242,5 +242,6 @@
 						savedSelection = savedScroll = null;
 						savedState = this.state;
-					}
+					},
+					canUndo : false
 				} );
 
Index: CKEditor/trunk/_source/plugins/preview/plugin.js
===================================================================
--- CKEditor/trunk/_source/plugins/preview/plugin.js	(revision 3607)
+++ CKEditor/trunk/_source/plugins/preview/plugin.js	(revision 3608)
@@ -13,5 +13,5 @@
 	{
 		modes : { wysiwyg:1, source:1 },
-
+		canUndo : false,
 		exec : function( editor )
 		{
Index: CKEditor/trunk/_source/plugins/print/plugin.js
===================================================================
--- CKEditor/trunk/_source/plugins/print/plugin.js	(revision 3607)
+++ CKEditor/trunk/_source/plugins/print/plugin.js	(revision 3608)
@@ -37,4 +37,5 @@
 			editor.document.$.execCommand( "Print" );
 	},
+	canUndo : false,
 	modes : { wysiwyg : !( CKEDITOR.env.opera ) }		// It is imposible to print the inner document in Opera.
 };
Index: CKEditor/trunk/_source/plugins/selection/plugin.js
===================================================================
--- CKEditor/trunk/_source/plugins/selection/plugin.js	(revision 3607)
+++ CKEditor/trunk/_source/plugins/selection/plugin.js	(revision 3608)
@@ -83,5 +83,6 @@
 					// TODO
 			}
-		}
+		},
+		canUndo : false
 	};
 
Index: CKEditor/trunk/_source/plugins/showblocks/plugin.js
===================================================================
--- CKEditor/trunk/_source/plugins/showblocks/plugin.js	(revision 3607)
+++ CKEditor/trunk/_source/plugins/showblocks/plugin.js	(revision 3608)
@@ -111,4 +111,5 @@
 		{
 			var command = editor.addCommand( 'showblocks', commandDefinition );
+			command.canUndo = false;
 
 			if ( editor.config.startupOutlineBlocks )