It was once possible to change the message a browser shows in the status bar at the bottom of the window. This functionality has been disabled in newer browser versions due
Using the browsers statusbar to display page info is in most cases a very bad idea, the browsers has not disabled it without reason.
Instead use somthing like the orange(yellow?) thing stackoverflow have at the top of the page. "Are you new to stackoverflow...", "New posts has been added..." etc etc.