// The client event Scrolled takes two parameters sender and e
// sender is the object which is raising the event
// e is the TabScrolledEventArgs
function WebTab1_Scrolled(sender, e) {
//Gets old scroll position in pixels as integer
var oldScroll = e.get_oldScroll();
//Gets new scroll position in pixels as integer
var newScroll = e.get_scroll();
//Assuming you have a label called labelOutput on the form
var label = $get('labelOutput');
label.innerHTML = "Successfully scrolled from '" + oldScroll + "px' to '" + newScroll + "px'!";
}