function auf(menu) 
{
if (document.getElementById)
{
document.getElementById(menu).style.visibility="visible";
}
if (document.all)
{
document.all[menu].style.visibility="visible";
}
if (document.layers)
{
document.layers[menu].visibility="visible";
}
}

function zu(menu) 
{
if (document.getElementById)
{
document.getElementById(menu).style.visibility="hidden";
}
if (document.all)
{
document.all[menu].style.visibility="hidden";
}
if (document.layers)
{
document.layers[menu].visibility="hidden";
}
}