function VerImagen(url){ 
	var ancho = 640;
	var alto = 480;
	if (arguments.length > 0) {
		ancho = arguments[1];
		alto = arguments[2];
	}
	var Lv_xposition=(screen.width  - ancho) / 2; // VENTANA CENTRADA
	var Lv_yposition=(screen.height - alto) / 2; //
	window.open( "/imagen.asp?img=" + url , 'imagen' , "width=" + ancho + ",height=" + alto + ",location=0,menubar=0,resizable=0,scrollbars=0,status=0,titlebar=0,toolbar=0,hotkeys=0,screenx=" + Lv_xposition + ",screeny=" + Lv_yposition + ",left=" + Lv_xposition + ",top=" + Lv_yposition); 
}