var objNewWindow = null;

function ventana(url, titulo, anchoAlto)
{
  var myModoWin = 'top=10, left=10, toolbar=no, menubar=no, location=no, directories=no, scrollbars=no';

  if( anchoAlto == '0,0')
    modoWin = myModoWin + ', width=800, height=800';
  else 
    modoWin = myModoWin + ', ' + anchoAlto;

	objNewWindow = window.open(url, titulo, modoWin);
	objNewWindow.focus()
}