var inner_el = null;

var outer_height = null;
var inner_height = null;

var current_scroll = 0;

function scrolldiv_init(outer_id, inner_id) {
	var outer_el = document.getElementById(outer_id);
	inner_el = document.getElementById(inner_id);
	
	outer_height = outer_el.offsetHeight;
	inner_height = inner_el.offsetHeight;
	
	window.setInterval("scrolldiv_scroll()", 50);
}

function scrolldiv_scroll() {
	if (current_scroll != 0 && outer_height < inner_height) {
		var current_top = inner_el.style.top;
		if (current_top == '') {
			current_top = 0;
		}
		else {
			current_top = parseInt(current_top);
		}
		current_top = current_top + current_scroll;
		if (current_top > 0) {
			current_top = 0;
		}
		else if (current_top < -(inner_height - outer_height)) {
			current_top = -(inner_height - outer_height);
		}
		inner_el.style.top = current_top + 'px';
	}
}

window.onload = function() {
	scrolldiv_init('scroll_outer', 'scroll_inner');
}