function openPreview(id){
	var previews = document.getElementsByTagName("div");

	for(var i=0; i<previews .length; i++){
          if(previews[i].className == "preview")
		previews [i].style.display = "none";
	}
	document.getElementById(id).style.display = 'block';
}

function closePreview(id){
	document.getElementById(id).style.display = 'none';
}