var UpdateInterval = 20;
var PixelPerInterval = 8;
var scorllerInterval = null;
function start_scroll_asagi() {
	scorllerInterval = setInterval(scroll_asagi, UpdateInterval);
}
function start_scroll_yukari() {
	scorllerInterval = setInterval(scroll_yukari, UpdateInterval);
}
function scroll_asagi() {
	document.getElementById('scroller').scrollTop += PixelPerInterval;
}
function scroll_yukari() {
	document.getElementById('scroller').scrollTop -= PixelPerInterval;
}
function stop_scrolling() {
	clearInterval(scorllerInterval);
}