Anything entered that is not an integer, when the data type is integer, it is considered less than (or in some cases equal to) 0 if I am not mistaken. This should also take care of it if a user enters nothing (which I'm pretty sure is considered as a value of 0).
No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.