function openPopup(url) {
	var width  = 735;
	var height = 448;
	/*var width  = screen.availWidth;
	var height = screen.availHeight;*/
	var left   = (screen.availWidth / 2)-(width/2);
	var top    = (screen.availHeight / 2)-(height/2);

	window.open(url,'ventana_pago',"menubar=no,location=no,toolbar=no,status=no,resizable=no,scrollbars=no,width="+ width +",height="+ height +",top="+ top +",left="+ left);
}