Problem with the script

Look at this menu http://ocanic.wsisiz.edu.pl/~jackowsj/zagle/menu.php
It works good at Mozilla and MS IE but in the OPERA 7.54 it's not working
and is not readable. This menu uses this script - look at this please and
tell me what do if I want it working under Opera web browser:

function lib_bwcheck(){ //Browsercheck (needed)
this.ver=navigator.appVersion
this.agent=navigator.userAgent
this.dom=document.getElementById?1:0
this.opera5=(navigator.userAgent.indexOf("Opera")> -1 && document.getElementById)?1:0
this.ie5=(this.ver.indexOf("MSIE 5")>-1 && this.dom && !this.opera5)?1:0;
this.ie6=(this.ver.indexOf("MSIE 6")>-1 && this.dom && !this.opera5)?1:0;
this.ie4=(document.all && !this.dom && !this.opera5)?1:0;
this.ie=this.ie4||this.ie5||this.ie6
this.mac=this.agent.indexOf("Mac")>-1
this.ns6=(this.dom && parseInt(this.ver) >= 5) ?1:0;
this.ns4=(document.layers && !this.dom)?1:0;
this.bw=(this.ie6 || this.ie5 || this.ie4 || this.ns4 || this.ns6 || this.opera5)
return this
}
var bw=lib_bwcheck()

/*** parametry kt�e mona konfigurowa�***/

FoldNumber = 5 //liczba link� g�nych
var stayFolded = false //zamkni�ie/otwarcie submenu po klikni�iu na link g�ny false/true
foldImg = 0 //liczba potrzebnych obrazk� (jeli wpiszesz 0, usu�obrazki z foldera)
mainOffsetY = 0 //odst� w pionie pomi�zy linkami w pixelach

//Domylny obrazek.
//Pami�aj o zmianie nazwy pliku jeli zamierzasz uy�innego obrazka
//var unImg=new Image();
//unImg.src='images/foldoutmenu_arrow.gif'

//var exImg=new Image(); //zmienna obrazka
//exImg.src='images/foldoutmenu_arrow_open.gif' //obrazek otwartego submenu

// NOTE: if you change the position of divCont from absolute to relative, you can put the foldoutmenu in a table.
// HOWEVER it will no longer work in netscape 4. If you wish to support netscape 4, you have to use absolute positioning.

/*** Nie zmienia�kodu poniej tej linii ***/

// Jednostki miary wyorzystane do pozycjonowania warstw.
var px = bw.ns4||window.opera?"":"px";

if(navigator.userAgent.indexOf('Opera')>-1 && document.getElementById){ //Opera 5 resize fix.
scrX= innerWidth; scrY= innerHeight;
document.onmousemove= function(){
if(scrX<innerWidth-10 || scrY<innerHeight-10 || scrX>innerWidth+10 || scrY>innerHeight+10){
scrX = innerWidth;
scrY = innerHeight;
initFoldout();
}
};
}

//konstrukcja obiekt�
function makeMenu(obj,nest){
nest= (!nest)?"":'document.'+nest+'.';
this.el= bw.ie4?document.all[obj]:bw.ns4?eval(nest+'document.'+obj):document.getEle mentById(obj);
this.css= bw.ns4?this.el:this.el.style;
this.ref= bw.ns4?this.el.document:document;
this.x= (bw.ns4||bw.opera5)?this.css.left:this.el.offsetLe ft;
this.y= (bw.ns4||bw.opera5)?this.css.top:this.el.offsetTop ;
this.h= (bw.ie||bw.ns6)?this.el.offsetHeight:bw.ns4?this.r ef.height:bw.opera5?this.css.pixelHeight:0;
this.vis= b_vis;
this.hideIt= b_hideIt;
this.showIt= b_showIt;
this.moveIt= b_moveIt;
return this
}
//metody obiekt�
function b_showIt(){this.css.visibility='visible'}
function b_hideIt(){this.css.visibility='hidden'}
function b_vis(){if(this.css.visibility=='hidden' || this.css.visibility=='HIDDEN' || this.css.visibility=='hide') return true;}
function b_moveIt(x,y){this.x=x; this.y=y; this.css.left=this.x+px; this.css.top=this.y+px}

/************************************************** **********************************
Funkcja zwijajca i rozwijajaca submenu
************************************************** **********************************/
function menu(num){
if(bw.bw){
if (!stayFolded){
for (var i=0; i<oSub.length; i++){
if (i!=num){
oSub[i].hideIt()
}
}
for(var i=1; i<oTop.length; i++){
oTop[i].moveIt(0,oTop[i-1].y+oTop[i-1].h)
}
}
if (oSub[num].vis()){
oSub[num].showIt()
}else{
oSub[num].hideIt()
}
for(var i=1; i<oTop.length; i++){
if (!oSub[i-1].vis()) oTop[i].moveIt(0,oTop[i-1].y+oTop[i-1].h+oSub[i-1].h+mainOffsetY)
else oTop[i].moveIt(0,oTop[i-1].y+oTop[i-1].h+mainOffsetY)
}
}
}

/************************************************** *******************
Funkcja inicjujca - niczego nie modyfikowa�
************************************************** *******************/
function initFoldout(){
//sprawdzenie wersji Opery
bw.opera5 = (navigator.userAgent.indexOf("Opera")>-1 && document.getElementById)?true:false
if (bw.opera5) bw.ns6 = 0

oTop = new Array()
oSub = new Array()
//tworzenie i ukrywanie
for (var i=0; i<FoldNumber; i++){
oTop[i] = new makeMenu('divTop'+i,'divCont')
oSub[i] = new makeMenu('divSub'+i,'divCont.document.divTop'+i)
oSub[i].hideIt()
}

//pozycjonowanie
oTop[0].moveIt(0,0)
for (var i=1; i<oTop.length; i++){
oTop[i].moveIt(0, oTop[i-1].y+oTop[i-1].h+mainOffsetY)
}

//wywietlanie
oCont = new makeMenu('divCont')
oCont.showIt()
}

//adowanie
if(bw.bw) onload = initFoldout;


--
******** Jacek Maria Jackowski POWERED BY FEDORA CORE 2 ********
* mail: jackowsj (AT) ANTYSPAMwsisiz (DOT) edu.pl ; gg:935481 *
* Linux is like a wigwame. No gates, no windows and apache inside *
************************************************** *****************

JavaScript console in Opera shows me that:
Event thread: onload
Error:
name: TypeError
message: Statement on line 57: Expression evaluated to null or undefined and is not convertible to Object: this.el
Backtrace:
Line 57 of linked script http://192.168.2.2/test/script/menu.js
this.css = bw.ns4 ? this.el : this.el.style;
Line 114 of linked script http://192.168.2.2/test/script/menu.js
oTop[i] = new makeMenu("divTop" + i, "divCont");
At unknown location
{event handler trampoline}
but I'm not js literate so I don't know what works wrong

--
******** Jacek Maria Jackowski POWERED BY FEDORA CORE 2 ********
* mail: jackowsj (AT) ANTYSPAMwsisiz (DOT) edu.pl ; gg:935481 *
* Linux is like a wigwame. No gates, no windows and apache inside *
************************************************** *****************