function showSubmenu() {

    var dropMenuElemStyle = document.getElementById('about').style;
    if (dropMenuElemStyle.display = "none") {
        dropMenuElemStyle.display = "block";
    }
}

function hideSubmenu() {

    var dropMenuElemStyle = document.getElementById('about').style;
    if (dropMenuElemStyle.display = "block") {
        dropMenuElemStyle.display = "none";
    }
}