function RotatingBillboard(id, duration)
{
	this.id = id;
	this.items = new Array();
	this.duration = duration;
	this.index = 0;
	return this;
}

RotatingBillboard.prototype.Register = function(id)
{
	var obj = document.getElementById(id);
	if(obj != null)
	{
		obj.style.display = 'none';
		this.items[this.items.length] = id;
	}
}

RotatingBillboard.prototype.Rotate = function()
{
	document.getElementById(this.items[this.index++]).style.display = 'none';
	if(this.index == this.items.length)
		this.index = 0;
	document.getElementById(this.items[this.index]).style.display = 'inline';
	setTimeout(this.id + '.Rotate()', this.duration);
}