It depends on the school. In most cases they'll still consider your application, but they'll mark in their file that it was late (and sometimes even put a color-coded sticker on your portfolio to mean that it didn't make the deadline.) There are some schools that will not consider a late application at all. If you're concerned about this you should call the school and ask about their policy.
As it is currently July and most deadlines are in December-February I'm curious as to what you're applying for right now?

Thanks for the info Aluminate.
I am an international student and have earlier deadlines for Grad School. So i want to know more about this application deadlines theory.

boskey - are you applying to arch schools? which ones? I am also an international student, and I remember that when I applied, the application deadlines were the same as domestic students. In general, I believe applications should be submitted on time, but you might be able to request an extension for letters of recommendation.