var ventana=false;

function Pop_UP(url, ancho, alto, titulo)
{
	
	if (typeof ventana.document == "object") {ventana.close()}	
	LeftPosition = (screen.width) ? (screen.width-ancho)/2 : 0;
	TopPosition = (screen.height) ? (screen.height-alto)/2 : 0;
	
	destino = "imagen.php?ruta=" + url + "&titulo=" + titulo;
	ventana = window.open(destino, "Imagen", "status = 1, left = " + LeftPosition + ", top = " + TopPosition + ", height = " + alto + ", width = " + ancho + ", resizable = 0" )
}