Problem with a scroll bar example from Kirupa

Hi there!
I am using an example from kirupa to create my scroll bar and everything related to it…
BUT, i am having a little bug… since my content is way longer than what the example offers it just doesnt work.

here is the www example from kirupa

While the example used in Kirupa has a main content high(y) of 990 the one that i am using has y=10200.
So when i am scrolling up and down, the down and the up doesnt work as expected.
Why is this happening?
PLS help!!!