// function to show/hide an element (or ns4 layer)
function showElement(strName, blnShow)
{
    // W3C dom compliant browsers (IE5, Mozilla etc.)
    if (document.getElementById)
    {
        document.getElementById(strName).style.visibility = 
            blnShow ? "visible" : "hidden";
        return;
    }
    // NS4 layers
    if (document.layers) 
    {
        document.layers[strName].visibility =
            blnShow ? "show" : "hide";
        return;
    }
    // Anything which supports document.all (IE4; some others like Konqueror)
    if (document.all)
        document.all[strName].visibility = 
            blnShow ? "visible" : "hidden";
}

// swap the main navigation
function mainNavigation(intImageNum) {
    
    showElement("show1", intImageNum == 1);
    showElement("show2", intImageNum == 2);
    showElement("show3", intImageNum == 3);
    showElement("show4", intImageNum == 4);
}