Need Quick JS Help

Hey, I'm trying to implement this script:
http://codylindley.com/Javascript/219/finding-a-javascript-tool-tip-script

But, for some reason, the JS won't work unless it is at the bottom of the page.

Can someone take a look plz. I wanna link to it externally.

//Edit the informaiton between the quotes below with the path to your image.
var imagePath = "images/tooltiparrow.gif";

function addwarning(){
var thealinks = document.getElementsByTagName("a");
if (!thealinks) { return; }

for(var x=0;x!=thealinks.length;x++){

if(thealinks[x].className == "addToolTip"){
thealinks[x].setAttribute("tooltiptext",thealinks[x].title);
thealinks[x].removeAttribute("title");
thealinks[x].onmouseover=function gomouseover(){ddrivetip(this.getAttribute("tooltiptext"))};
thealinks[x].onmouseout=function gomouseout(){hideddrivetip();};
}
}
}

var offsetfromcursorX=-7; //Customize x offset of tooltip
var offsetfromcursorY=23; //Customize y offset of tooltip

var offsetdivfrompointerX=13; //Customize x offset of tooltip DIV relative to pointer image
var offsetdivfrompointerY=13; //Customize y offset of tooltip DIV relative to pointer image. Tip: Set it to (height_of_pointer_image-1).

document.write('<div id="theToolTip"></div>'); //write out tooltip DIV
document.write('<img id="ToolTipPointer" src="'+imagePath+'">'); //write out pointer image

var ie=document.all;
var ns6=document.getElementById && !document.all;
var enabletip=false;
if (ie||ns6) {
	var tipobj=document.all? document.all["theToolTip"] : document.getElementById? document.getElementById("theToolTip") : "";
}

var pointerobj=document.all? document.all["ToolTipPointer"] : document.getElementById? document.getElementById("ToolTipPointer") : "";

function ietruebody(){
return (document.compatMode && document.compatMode!="BackCompat")? document.documentElement : document.body;
}

function ddrivetip(thetext, thewidth, thecolor){
if (ns6||ie){
if (typeof thewidth!=="undefined") {tipobj.style.width=thewidth+"px";}
if (typeof thecolor!=="undefined" && thecolor!=="") {tipobj.style.backgroundColor=thecolor;}
tipobj.innerHTML=thetext;
enabletip=true;
return false;
}
}

function positiontip(e){
if (enabletip){
var nondefaultpos=false;
var curX=(ns6)?e.pageX : event.clientX+ietruebody().scrollLeft;
var curY=(ns6)?e.pageY : event.clientY+ietruebody().scrollTop;
//Find out how close the mouse is to the corner of the window
var winwidth=ie&&!window.opera? ietruebody().clientWidth : window.innerWidth-20;
var winheight=ie&&!window.opera? ietruebody().clientHeight : window.innerHeight-20;

var rightedge=ie&&!window.opera? winwidth-event.clientX-offsetfromcursorX : winwidth-e.clientX-offsetfromcursorX;
var bottomedge=ie&&!window.opera? winheight-event.clientY-offsetfromcursorY : winheight-e.clientY-offsetfromcursorY;

var leftedge=(offsetfromcursorX<0)? offsetfromcursorX*(-1) : -1000;

//if the horizontal distance isn't enough to accomodate the width of the context menu
if (rightedge<tipobj.offsetWidth){
//move the horizontal position of the menu to the left by it's width
tipobj.style.left=curX-tipobj.offsetWidth+"px";
nondefaultpos=true;
}
else if (curX<leftedge)
{tipobj.style.left="5px";}
else{
//position the horizontal position of the menu where the mouse is positioned
tipobj.style.left=curX+offsetfromcursorX-offsetdivfrompointerX+"px";
pointerobj.style.left=curX+offsetfromcursorX+"px";
}

//same concept with the vertical position
if (bottomedge<tipobj.offsetHeight){
tipobj.style.top=curY-tipobj.offsetHeight-offsetfromcursorY+"px";
nondefaultpos=true;
}
else{
tipobj.style.top=curY+offsetfromcursorY+offsetdivfrompointerY+"px";
pointerobj.style.top=curY+offsetfromcursorY+"px";
}
tipobj.style.visibility="visible";
if (!nondefaultpos) {pointerobj.style.visibility="visible";}
else{
pointerobj.style.visibility="hidden";}
}
}

function hideddrivetip(){
if (ns6||ie){
enabletip=false;
tipobj.style.visibility="hidden";
pointerobj.style.visibility="hidden";
tipobj.style.left="-1000px";
tipobj.style.backgroundColor='';
tipobj.style.width='';
}
}

document.onmousemove=positiontip;
addwarning();

Code (markup):

 

erm.

function addwarning(){
var thealinks = document.getElementsByTagName("a");
if (!thealinks) { return; }

PHP:

if you put that script at the top, the links won't be defined yet, hence this will just exit. this is why you need a document.onload / domready / load handler (depends on what framework you use) - it's a way of delaying js execution so that all elements of the DOM are available.

running it at the bottom gives it some A elements to work with...

 

just examples:

jQuery:

$(function()
{
       your code
});

PHP:

ExtJS:

Ext.onReady(function()
{
      your_code
});

PHP:

GL.