How is this site preforming an action when you get to a certain part of the page?
I went to a website http://wishbone.org/ and when you get to a graphic of a bunch of cartoon people it changes color, but it starts when you reach it. There's not predetermined time. How do they do that?
The trick is to handle "scroll" events and wait for a a particular element to become visible, or for the scroll "top" distance to reach a certain minimum.