Using AJAX in vBulletin 4.0

[AcoDe]

Hello all,
Some body can explain how do i use AJAX (post method) in vBulletin 4.0
I know how to handle ajax normaly and in vBulletin 4.0 it's deffrent.
So, i will be more than glad to know how to use it in vBulletin 4.0.

Thanks a head,
Hagai.