window.onload = function () {
    var navigationDiv = document.getElementById('nav');
    var navigationUl = false;
    navigationUl = sucheUL(navigationDiv.firstChild);

    var LI = navigationUl.firstChild;
    do {
        if (sucheUL(LI.firstChild)) {
            LI.onmouseover=einblenden; 
            LI.onmouseout=ausblenden;
        }
        LI = LI.nextSibling;
    } while(LI);
}

function sucheUL(UL) 
{
    while (UL) {
        if(UL && UL.nodeName == "UL") return UL;
        if(UL) UL = UL.nextSibling;
    } 
    return false;
}

function einblenden() 
{
    var UL = sucheUL(this.firstChild);
    UL.style.display = "block"; 
}

function ausblenden() 
{
    sucheUL(this.firstChild).style.display = "none";
}