Understanding Checker Deselect I don't succeed in selecting a group of faces and deselect with Checker Deselect. 

Consider a cube that has been looped cut ...

Select all the faces of the top side ...



Click on Checker Deselect ...



What does it mean ?

(I am using v2.78c)
You need to have an active face. This is a way to give an indication to Blender in order to control which faces will be kept selected:



If no face is active, you obtain the message mentioned in your question.