var activeMenu = null;

function hideActive() 
{
    if (activeMenu !== null) 
    {
        hideIt(activeMenu);
        activeMenu = null;
    }
}

function popMenu(obj) 
{
    hideActive();
    activeMenu = document.getElementById(obj);
    showIt(activeMenu);
}

function hideIt(obj) 
{
    obj.style.visibility = "hidden";
}

function showIt(obj) 
{
    obj.style.visibility = "visible";
}