This very simple trigger (I've given it two names but its the same idea) is to detect if a msg box has already opened or not in the users session.

I have various triggers setup in an account that work on specific page urls in my site and I don't want to over do it with too many msgs from triggers if the user is quite active and reads too many of these pages.

So it's that simple, the idea of the trigger is to stop too many prompts being sent. The condition checks if there has been any activity at all (even if its just triggers sent on previous pages).