var originalClassName = "";

function ShowDropDownMenu(parentElementID, elementID) {
    var parentElement = document.getElementById(parentElementID);
    var dropdown = document.getElementById(elementID);
    if (dropdown.style.visibility == 'visible') {
        return;
    }
    dropdown.style.visibility = 'visible';
    originalClassName = parentElement.className;
    parentElement.className = "on";
}

function HideDropDownMenu(parentElementID, elementID) {
    var parentElement = document.getElementById(parentElementID);
    var dropdown = document.getElementById(elementID);
    if (dropdown.style.visibility == 'hidden') {
        return;
    }
    dropdown.style.visibility = 'hidden';
    parentElement.className = originalClassName;
}