var offsetfromedge = 0 //offset from window edge when content is "docked". Change if desired.
    var dockarray = new Array() //array to cache dockit instances
    var dkclear = new Array() //array to cache corresponding clearinterval pointers

/***********************************************
* Dock Content script- Created by and © Dynamicdrive.com
* This notice must stay intact for use
* Visit http://www.dynamicdrive.com/ for full script
***********************************************/

function dockit(el, duration) {
  //this.source = document.all ? document.all[el] : document.getElementById(el);
  this.source = document.getElementById(el);
  this.source.height = this.source.offsetHeight;
  this.docheight = truebody().clientHeight;
  this.duration = duration;
  this.pagetop = 0;
  this.elementoffset = this.getOffsetY();
  dockarray[dockarray.length] = this;

  var pointer = eval(dockarray.length - 1);
  var dynexpress = 'dkclear[' + pointer + '] = setInterval("dockornot(dockarray[' + pointer + '])",100);';

  dynexpress = (this.duration > 0) ? dynexpress + 'setTimeout("clearInterval(dkclear[' + pointer + ']); dockarray[' + pointer + '].source.style.top = 0", duration*1000)' : dynexpress;
  eval(dynexpress);
}

dockit.prototype.getOffsetY = function() {
  var totaloffset = parseInt(this.source.offsetTop);
  var parentEl = this.source.offsetParent;
  
  while (parentEl != null){
    totaloffset += parentEl.offsetTop;
    parentEl = parentEl.offsetParent;
  }

  return totaloffset;
}

function dockornot(obj){
  obj.pagetop = truebody().scrollTop;
  
  if (obj.pagetop > obj.elementoffset) //detect upper offset
    obj.source.style.top = obj.pagetop - obj.elementoffset + offsetfromedge + "px";
//  else if (obj.pagetop + obj.docheight < obj.elementoffset + parseInt(obj.source.height)) //lower offset
//    obj.source.style.top = obj.pagetop + obj.docheight - obj.source.height - obj.elementoffset - offsetfromedge + "px";
  else
    obj.source.style.top = 0;
}

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