var count_menu = 6;
var menu_images  = new Array();

for (i=1; i<=count_menu; i++) {
    menu_images[i]     = new Image();
    menu_images[i].src = "images/navigation/"+i+"on.gif";
}

function menu_on (id)
{
    if (document.getElementById) {
        if (document.getElementById("menu"+id) && 
            !document.getElementById("menu"+id).src.match(/active\.gif$/)) {
            
            document.getElementById("menu"+id).src = "images/navigation/"+id+"on.gif";
        }
    }
}

function menu_off (id)
{
    if (document.getElementById) {
        if (document.getElementById("menu"+id) && 
            !document.getElementById("menu"+id).src.match(/active\.gif$/)) {
                
            document.getElementById("menu"+id).src = "images/navigation/"+id+"off.gif";
       }
    }
}