function popup(picture, width, height)
{
	var window_width = width;
	var window_height = height;
	window_posx = (screen.availWidth - window_width) / 2; 
	window_posy = (screen.availHeight - window_height) / 2;

	var windowprops = "screenX="+window_posx+",left="+window_posx+",screenY="+window_posy+",top="+window_posy+", width="+window_width+",height="+window_height;
	var URL = 'http://www.textile-collection.nl/fotos/' + picture + '.jpg';
	thumbWin = window.open(URL,'popup',windowprops);
}