var scroll_speed = 10; // pixels
var scroll_timer;

function scroll_up() {
	var container = document.getElementById('scroll_container');
	var content = document.getElementById('scroll_content');
	
	if (!content.style.top) content.style.top = '0px';

	var visible = container.offsetHeight; // altura do conteúdo visível
	var total = content.offsetHeight; // altura do conteúdo total
	
	var unvisible = total - visible + parseInt(content.style.top); // altura do conteúdo restante
	
	if (parseInt(content.style.top) < 0) {
		content.style.top = parseInt(content.style.top) + scroll_speed + "px";
	}
	
	scroll_timer = setTimeout("scroll_up()", 100);
}

function scroll_down() {
	var container = document.getElementById('scroll_container');
	var content = document.getElementById('scroll_content');
	
	if (!content.style.top) content.style.top = '0px';
	
	var visible = container.offsetHeight; // altura do conteúdo visível
	var total = content.offsetHeight; // altura do conteúdo total
	
	var unvisible = total - visible + parseInt(content.style.top); // altura do conteúdo restante
	
	if (parseInt(content.style.top) >= ((total - visible) * (-1)) && unvisible) {
		content.style.top = parseInt(content.style.top) - scroll_speed + "px";
	}
	
	scroll_timer = setTimeout("scroll_down()", 100);
}

function scroll_stop() {
	clearTimeout(scroll_timer);
}