Some if not most developers have known about this, so the superstitious 13th floor would have been removed from the lift button panel. The 13th floor is considered as a "bad floor" especially in Western countries. In Malaysia, the number 4 is considered as "bad" too. So, specifically apartments or buildings built by Chinese developers, some of the levels with the number 13 and 4 are renamed. I have noticed some offices have renamed 13 and 14 floor to 12A and 12B respectively. So it goes like this:-

9
10
11
12
12A
12B
15
16
17

As I mentioned in another thread earlier, the "unlucky" floors may be harder to sell, but in the end you will still see people filling up these floors sooner or later.