function blocking(x) {
        if (document.layers)
        {
                current = (document.layers[x].display == 'none') ? 'block' : 'none';
                document.layers[x].display = current;
        }
        else if (document.all)
        {
                current = (document.all[x].style.display == 'none') ? 'block' : 'none';
                document.all[x].style.display = current;
        }
        else if (document.getElementById)
        {
                vista = (document.getElementById(x).style.display == 'none') ? 'block' : 'none';
                document.getElementById(x).style.display = vista;
        }
}