function	ventana(url, winName, width, height, opciones) {


	if ( navigator.appName == "Netscape" ) {
	
	
		var top 	= window.screenY + ((window.outerHeight - height) / 2);

		var left 	= window.screenX + ((window.outerWidth - width) / 2);

		var attr 	= ',screenX=' + left + ',screenY=' + top;


	} else if ( document.all ) {
		

		var top 	= (screen.height - height) / 2;
		
		var left 	= (screen.width - width) / 2;

		var attr 	= ',left=' + left + ',top=' + top;
		

	}

	
	opciones = 'width=' + width + ',height=' + height + attr + opciones;
	

	window.open(url, winName, opciones);


}