function menuOn()
{
    document.getElementById("midmenu_1").style.visibility = 'hidden';
    document.getElementById("midmenu_2").style.visibility = 'hidden';
    document.getElementById("midmenu_3").style.visibility = 'hidden';
    document.getElementById("midmenu_4").style.visibility = 'hidden';
}

function menuOff()
{
    document.getElementById("midmenu_1").style.visibility = 'visible';
    document.getElementById("midmenu_2").style.visibility = 'visible';
    document.getElementById("midmenu_3").style.visibility = 'visible';
    document.getElementById("midmenu_4").style.visibility = 'visible';
}