function ventana(URL,h,w) {

	x=(screen.availWidth)
	y=(screen.availHeight)-30
	

	posx=(x/2-w/2);
	posy=(y/2-h/2);
	day = new Date();
	id = day.getTime();
	eval("page" + id + " = window.open(URL, '" + id + "', 'toolbar=0,scrollbars=0,location=0,statusbar=0,menubar=0,resizable=0,width="+w+",height="+h+",left="+posx+",top="+posy+"');");
}