Some Doubt in C Socket

[marktianyi]

First,I makes one program to scan the destination host port. But I found some interesting in it.
The destination host is open 80 port. When the program scan 0 ~ 80 port so slowly [1~2 Seconds one port]. Then after 80 port,the program scan so fast [one seconds 100~200 port].
What is this so?

[hanst99]

Security reasons.

http://www.iana.org/assignments/port-numbers