Error with Java Script in IE 8

if (l.hilite) {
            l.document.bgColor = l.menuHiliteBgColor;
            l.zIndex = 1;
            l.hilite.visibility = "inherit";
            l.hilite.zIndex = 2;
            l.document.layers[1].zIndex = 1;
            l.focusItem.zIndex = this.zIndex +2;
        }
        l.focusItem.top = this.top;
        l.Menu.hideChildMenu(l);
    } else if (document.all && l.style && l.Menu) {
        document.onmousedown=l.Menu.onMenuItemDown;
        if (a) {
            a.style.backgroundColor = a.saveColor;
            if (a.hilite) a.hilite.style.visibility = "hidden";
        } else {
            a = new Object();
		}
        if (l.mouseover && l.id != a.id) {
            if (l.mouseover.length > 4) {
                var ext = l.mouseover.substring(l.mouseover.length-4);
                if (ext == ".gif" || ext == ".jpg") {
                    l.document.images[l.id + "Img"].src = l.mouseover;
                } else {
                    eval("" + l.mouseover);
                }
            }
        }
		if (l.isSeparator) return;
        l.style.backgroundColor = l.menuHiliteBgColor;
        if (l.hilite) {
            l.style.backgroundColor = l.menuHiliteBgColor;
            l.hilite.style.visibility = "inherit";
        }
        l.focusItem.style.pixelTop = l.style.pixelTop;
        l.focusItem.style.zIndex = l.zIndex +1;           <------Error Line
        l.zIndex = 1;
        l.Menu.hideChildMenu(l);
    } else if (document.getElementById){
        document.onmousedown=l.Menu.onMenuItemDown;	
        if (a) {
	        a.style.backgroundColor = a.saveColor;
    	    if (a.hilite) a.hilite.style.visibility = "hidden";
        } else {
            a = new Object();
        }
        if (this.mouseover && this.id != a.id) {
            if (this.mouseover.length > 4) {
                var ext = this.mouseover.substring(this.mouseover.length-4);
                if (ext == ".gif" || ext == ".jpg") {
                    document.images[l.id + "Img"].src = this.mouseover;
                } else {
                    eval("" + this.mouseover);
                }
            }
        }

                                  

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