Script funkt im IE 3 nicht

[OPPATRIA]

Das folgende Script für eine neue Menuleiste krieg' ich im IE 3 einfach nicht zum laufen:

<script language="JavaScript">
function navItem (name, num, base, width, height) {
      this.over = new Image();
      this.over.src = "images/" + name + "on.gif";
      this.out = new Image();
      this.out.src = "images/" + name + "off.gif";
      this.set = new Image();
      this.set.src = "images/" + name + "set.gif";
      this.base = base;
      this.num = num;
}

function nav_new (name,num,base) {
      navItem[name] = new navItem(name,num,base);
}

function img_over (imgName) {
    if (document.images) {
        if (document [imgName].src != navItem[imgName].set.src) {
                document[imgName].src = navItem[imgName].over.src;
        }
    }
}

function img_out (imgName) {
    if (document.images) {
        if (document [imgName].src != navItem[imgName].set.src) {
                document [imgName].src = navItem[imgName].out.src;
        }
    }
}

function img_set (imgName) {
    if (document.images) {
                document ['nav1'].src = navItem['nav1'].out.src;
                document ['nav2'].src = navItem['nav2'].out.src;
                document ['nav3'].src = navItem['nav3'].out.src;
                document ['nav4'].src = navItem['nav4'].out.src;
                document ['nav5'].src = navItem['nav5'].out.src;
                document ['nav6'].src = navItem['nav6'].out.src;
                document ['nav7'].src = navItem['nav7'].out.src;
                document ['nav8'].src = navItem['nav8'].out.src;
                document ['nav9'].src = navItem['nav9'].out.src;
                document ['nav10'].src = navItem['nav10'].out.src;
            document [imgName].src = navItem[imgName].set.src;
    }
}

function load_nav (name, num) {
        for (i = 1; i <= num; i++) nav_new(name + i,num,name);
}

if (document.images != null) load_nav ('nav', 10);

</script>

Kann mir jemand helfen ??

Danke

OPPS