function showPhoto (photo_id) {
	if (gCurrentPhoto != null) {
		photoToHide = document.getElementById(gCurrentPhoto);
		photoToHide.style.visibility = "hidden";
	}
	
	photoToShow = document.getElementById(photo_id);
	photoToShow.style.visibility = "visible";
	gCurrentPhoto = photo_id;
}

gCurrentPhoto = "photo1";