window.onload=rollup;

function rollout(objMenuitem)
{
    if (objMenuitem.nextSibling.style.display == 'block')
        objMenuitem.nextSibling.style.display = 'none';
    else
        objMenuitem.nextSibling.style.display = 'block';

    // Stop the browser requesting the link
    return false;
}

function rollup()
{
    var objNode, objAnchor;

    // Check we're working with a DOM compliant browser
    if (document.getElementById && document.createElement)
    {
        var objMenu = document.getElementById('mainnav');

        var objNested = objMenu.getElementsByTagName('ul');

        // Hide each of the nested unordered list
        for (var i=0; i<objNested.length; i++)
        {
            objNested[i].style.display = 'none';

            // Place the top-level text in an anchor tag
            objNode = objNested[i].parentNode;

            strContent = objNode.firstChild.data;

            objAnchor = document.createElement('a');
            objAnchor.href = '#';
            objAnchor.onclick = function(){return rollout(this);}
            objAnchor.appendChild(document.createTextNode(strContent));

            objNode.replaceChild(objAnchor, objNode.firstChild);
        }
    }
}