function showDrop(n) {
    var ypos;
    ypos = document.getElementById('nav_item' + n).offsetTop;
    document.getElementById('subnav_grp' + n).style.top = ypos + 'px';
    document.getElementById('subnav_grp' + n).style.display = 'block'; }

function holdDrop(n) {
    document.getElementById('subnav_grp' + n).style.display = 'block'; }

function hideDrop(n) {
    document.getElementById('subnav_grp' + n).style.display = 'none'; }