function scrollup() {
	var item = getElementByClass('contents');
	if (item != null) {
		item.scrollTop = item.scrollTop - 30;
	}
}

function scrolldown() {
	var item = getElementByClass('contents');
	if (item != null) {
		item.scrollTop = item.scrollTop + 30;
	}
}

function getElementByClass(elementClassName) {
	var items = document.getElementsByTagName("div");
	var item = null;
	for (i = 0; i < items.length; i++) {
  	if (items[i].className == elementClassName)
   	{
   		item = items[i];
   		break;
   	}
	}
	return item;
}