Hello Nigel,
that icon appears when an object has had its Style settings changed, so you hmay have set, for example, a background image for it.

Eric

Thanks for clarifying Eric. 

When same tool to add personal infos on each object into the page, and to add also a earch option to find any comments into this option ????

Already asked as idea ? but just a user idea and not Incomedia idea which is always better