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

function dockit(el, duration){
    this.source=document.all? document.all[el] : 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+'], \''+ el +'\')",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, el){
    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
}