function openMenu(id) {
        subnavi = document.getElementById('sub1');
        subnavi.style.display="none";
        subnavi = document.getElementById('sub2');
        subnavi.style.display="none";
        subnavi = document.getElementById('sub3');
        subnavi.style.display="none";
        subnavi = document.getElementById('sub4');
        subnavi.style.display="none";
        subnavi = document.getElementById('sub5');
        subnavi.style.display="none";
        subnavi = document.getElementById('sub6');
        subnavi.style.display="none";
        subnavi = document.getElementById(id);
        subnavi.style.display="block";
}