whats wrong with this code...please help newbie

[newwebprogramer]

*/

function addEvent(object, evName, fnName, cap) {
if (object.attachEvent)
object.attachEvent("on" + evName, fnName);
else if (object.addEventListener)
object.addEventListener(evName, fnName, cap);
}

addEvent(window, "load", makeTOC, false);

var sections = new Array("h1", "h2", "h3", "h4", "h5", "h6");
var sourceDoc; // document on which the TOC is based

function makeTOC() {
var TOC = document.getElementById("toc");
TOC.innerHTML = "<h1>Table of Contents</h1>";
var TOCList = document.createElement("ol");
TOC.appendChild(TOCList);

sourceDoc = document.getElementById("doc");

// generate list items containing section headings
createList(sourceDoc, TOCList);
}

function levelNum(node) {
for (var i = 0; i < sections.length; i++) {
if (node.nodeName == sections[i].toUpperCase()) return i;
}
return -1; // node is not a section heading
}

function createList(object, list) {

var prevLevel = 0; // level of the previous TOC entry
var headNum = 0; // running count of section headings

for (var n = object.firstChild; n != null; n = n.nextSibling) {
// loop through all of the nodes within object

var nodeLevel = levelNum(n);
if (nodeLevel != -1) {
// node represents a section heading

//insert id for the section heading if necessary
headNum++;
if (n.id == "") {n.id = "head" + headNum;}

// create a list item to match
var listItem = document.createElement("li");

// Create a hypertext link to the section heading
var linkItem = document.createElement("a");
linkItem.innerHTML = n.innerHTML;
linkItem.href = "#" + n.id;

// Append the hypertext link to the list entry
listItem.appendChild(linkItem);

if (nodeLevel == prevLevel) {
// append the entry to the current list
list.appendChild(listItem);
}

else if (nodeLevel > prevLevel) {
// append the entry to a new nested list
var nestedList = document.createElement("ol");
nestedList.appendChild(listItem);

list.lastChild.appendChild(nestedList);

// Add plus/minus box before the text of the nested list
var plusMinusBox = document.createElement("span");
plusMinusBox.innerHTML = "--";
addEvent(plusMinusBox, "click", expandCollapse, false);
nestedList.parentNode.insertBefore(plusMinusBox, nestedList.previousSibling);
list = nestedList;
prevLevel = nodeLevel;
}

else if (nodeLevel < prevLevel) {
// append the entry to a higher-level list
var levelUp = prevLevel - nodeLevel;
for (var i = 1; i <= levelUp; i++) {list = list.parentNode.parentNode;}

list.appendChild(listItem);
prevLevel = nodeLevel;

}
}

}
}

function expandCollapse(e) {
var plusMinusBox = e.target || event.srcElement;
var nestedList = plusMinusBox.nextSibling.nextSibling;

// Toggle the plus and minus symbol
if (plusMinusBox.innerHTML == "--") plusMinusBox.innerHTML = "+"
else plusMinusBox.innerHTML = "--";

// Toggle the display style of the nested list
if (nestedList.style.display == "none") nestedList.style.display = ""
else nestedList.style.display = "none";

// expand and collapse the source document to match the TOC
expandCollapseDoc();
}

function expandCollapseDoc() {
var displayStatus = "";
for (var n = sourceDoc.firstChild; n != null; n = n.nextSibling) {
var nodeLevel = levelNum(n);

if (nodeLevel != -1) {
// determine the display status of the TOC entry
var TOCentry = document.getElementById("TOC" + n.id);
if (isHidden(TOCentry)) displayStatus = "none"
else displayStatus = "";
}

if (n.nodeType == 1) { // node represents a page element
// apply the current display status to the node
n.style.display = displayStatus;
}
}
}

function isHidden(object) {
for (var n = object; n.nodeName != "BODY"; n = n.parentNode) {
if (n.style.display == "none") return true;
}

return false;
}