var viewer_delay = 10;
var viewer_direct = 0;
var viewer_delta = 2;
var viewer_y = 0;
var viewer_idInterval=null;

function move_site_up()
{//alert("start");
	if(viewer_idInterval!=null || !check(1))
		return;

	viewer_direct = 1;
	el = document.getElementById("sites");
	viewer_idInterval = setInterval("refresh()", viewer_delay);
	
}

function move_site_down()
{
	if(viewer_idInterval!=null || !check(2))
		return;

	viewer_direct = 2;
	el = document.getElementById("sites");
	viewer_idInterval = setInterval("refresh()", viewer_delay);
}

function finish_move()
{
	//alert("finish");
	if(viewer_idInterval!=null)
	{
		clearInterval(viewer_idInterval);
		viewer_idInterval = null;
		viewer_direct = 0;
	}
}

function refresh()
{
	if(viewer_direct==1)
	{
		viewer_y = viewer_y - viewer_delta;
		el.style.top = viewer_y + "px";
	}
	
	if(viewer_direct==2)
	{
		viewer_y = viewer_y + viewer_delta;
		el.style.top = viewer_y + "px";
	}
	
	if(!check(viewer_direct))
			finish_move();
}

function check(dir)
{
	if(dir==1)
	{
		if(viewer_y<-310)
			return false;
	}
	
	if(dir==2)
	{
		if(viewer_y>=0)
			return false;
	}
	
	return true;
}