Here is the code snippet:

 
var numOrbs=50;       //number of Orbs
var iv=.7;            //initial Orb speed
var Orbcollisions=1;    //Orb collisions 1=on, 0=off
var Zeye;           //perspective:distance of eye from box centre
var Zscreen;           //perspective:distance of screen from box centre
var pw,ph,cw,ch;
var Orbsize,Orbsize2;
var xmin,ymin,xmax,ymax,zmin,zmax;
var collisions=new Array();
var collisionpool= new Array();
var vx=new Array();
var vy=new Array();
var vz=new Array();
var px=new Array();
var py=new Array();
var pz=new Array();
var cln=new Array();
var Orb=new Object();
var twa;
var eps=0.01;
var alarm=0;
var offsetx;
var offsety;
var os
function init(){
 var i,im,theta;
  Orbsize=25;
  Orbsize2=4*Orbsize*Orbsize;
  for(i=0;i<numOrbs*2;i++)collisionpool.push(new collision(container));
 resize()  
  for(i=0;i<numOrbs;i++){
   var i,im,theta;
    cln[i]=new Array;
    for(j=0;j<numOrbs;j++)cln[i][j]=0;
    px[i]=-.5*cw;
    py[i]=-.5*ch;
    pz[i]=(zmin);
    theta=Math.PI*2*Math.random();
    phi=Math.asin(Math.random());
    //if(Math.random()>0.5)phi=-phi;
    vx[i]=iv*Math.cos(theta)*Math.cos(phi);
    vy[i]=iv*Math.sin(theta)*Math.cos(phi);
    vz[i]=iv*Math.sin(phi);
  Orb[i]=new OrbCreator(i);
  Orb[i+50]=new OrbCreator(i+50);
  Orb[i+100]=new OrbCreator(i+100);
  }
  document.body.onresize=resize;
  setInterval("anim();",100);
}
 
function OrbCreator(ID){
  var b;
 b=document.createElement("<img src='./images/Orb.png' style='position:absolute; display:none; left:10000px; top:0px; width:"+(2*Orbsize)+"px; height:"+(2*Orbsize)+"px;'>");
 this.is=b.style;
  this.move=moveOrb;
  document.getElementById("container").appendChild(b);
 this.is.display='block';
 this.is.id=ID;
}
 

	
	
 
function moveOrb(x,y,z){
 k=(Zeye-Zscreen)/(Zeye-z);
 os=(Orbsize*k);
 x=x-os;
 y=y-os;
 var OS=os*2;
  this.is.width=OS;
  this.is.height=OS;
  this.is.left=x;
  this.is.top=y;
  this.is.zIndex=z;
 //if(document.getElementById('message').style.top>0)document.getElementById('message').style.top=document.getElementById('message').style.top-1;
}
here is the calling code:
   Orb[a].move(px[a],py[a],pz[a]);
   Orb[a+50].move(px[a],(px[a]+offsetx),pz[a]);
   Orb[a+100].move(px[a],(py[a]+offsety),pz[a]);

When I declare Orb as an Array, no problem...
When I declare Orb as an Object, moveOrb() throws the error "Invalid argument"... What's up?

Am I correct in my understanding that Array is a predefined Object and is really not much different than a defined argument?

No - In my understanding an array is much different than an object. An array is numerically indexed and an object is namedspaced.

Hmm, good point.