function displaySubMenu(li) {
    var subMenu = li.getElementsByTagName("div")[0];
    subMenu.style.display = "block";

}
function hideSubMenu(li) {
    var subMenu = li.getElementsByTagName("div")[0];
    subMenu.style.display = "none";

}

function displayAlt(num) {
    for (i = 1; i <= 4; i++) {
        var tab = 'tab0' + i;
        var obj = document.getElementById(tab);

        if (i == num) {
            obj.style.display = 'block';
        } else {
            obj.style.display = 'none';
        }
    }

    var img01 = document.getElementById('img01');
    var img02 = document.getElementById('img02');
    var img03 = document.getElementById('img03');
    var img04 = document.getElementById('img04');
    if (num == 1) {
        img01.src = 'images/tab01.jpg';
        img02.src = 'images/tab02_2.jpg';
        img03.src = 'images/tab03_2.jpg';
        img04.src = 'images/tab04_2.jpg';
    } else if (num == 2) {
        img01.src = 'images/tab01_1.jpg';
        img02.src = 'images/tab02.jpg';
        img03.src = 'images/tab03_1.jpg';
        img04.src = 'images/tab04_1.jpg';
    } else if (num == 3) {
        img01.src = 'images/tab01_3.jpg';
        img02.src = 'images/tab02_3.jpg';
        img03.src = 'images/tab03.jpg';
        img04.src = 'images/tab04_1.jpg';
    }
    else if (num == 4) {
        img01.src = 'images/tab01_4.jpg';
        img02.src = 'images/tab02_4.jpg';
        img03.src = 'images/tab03_4.jpg';
        img04.src = 'images/tab04.jpg';
    }

}