function update_scrollbar()
  {

	if(objScroller.y>=0){ 
	// bovenkant van div bereikt, dus cursor default en plaatje grijs
    document.getElementById("link_pijl_op").style.cursor = 'default';
    document.getElementById("pijl_op").src="images/scrollbar_01.gif";}
	else
	{document.getElementById("link_pijl_op").style.cursor = 'hand';
    document.getElementById("pijl_op").src="images/scrollbar_01b.gif";}
	
    if(objScroller.y<=-objScroller.scrollHeight+objContainer.clipHeight){ 
	// onderkant van div bereikt, dus cursor default en plaatje grijs
    document.getElementById("link_pijl_neer").style.cursor = 'default';
    document.getElementById("pijl_neer").src="images/scrollbar_03.gif";}
	else
    {
    document.getElementById("link_pijl_neer").style.cursor = 'hand';
	document.getElementById("pijl_neer").src="images/scrollbar_03b.gif";}

	if (typeof window.v_scrollbar == "undefined") 
	{v_scrollbar='auto';}
	
	if ((objScroller.scrollHeight<=objContainer.clipHeight||v_scrollbar=='off')&&v_scrollbar!='on')
	{
	document.getElementById("div_link_pijl_op").style.visibility='hidden';
	document.getElementById("div_scrollbar").style.visibility='hidden';
	document.getElementById("div_scrollbar_line").style.visibility='hidden';
	document.getElementById("div_link_pijl_neer").style.visibility='hidden';
	}
	document.getElementById("div_scrollbar_line").style.visibility='hidden';
	
/*    ypos=-objScroller.y/(-objScroller.scrollHeight+objContainer.clipHeight);
    ypos=4+document.getElementById("div_scrollbar").offsetTop-ypos*parseInt(document.getElementById("div_scrollbar").style.height);
    document.getElementById("div_scrollbar_line").style.top=ypos;
	*/  
  }
	

function boven(){
objScroller.MoveArea(0,0);
update_scrollbar();
}

function anker(id){
y=document.getElementById(id).offsetTop;
objScroller.MoveArea(0,-y);
update_scrollbar();
}

function beneden(){
objScroller.MoveArea(0,-objScroller.scrollHeight+objContainer.clipHeight);
update_scrollbar();
}

function verifyCompatibleBrowser(){ 
    this.ver=navigator.appVersion 
    this.dom=document.getElementById?1:0 
    this.ie5=(this.ver.indexOf("MSIE 5")>-1 && this.dom)?1:0; 
    this.ie4=(document.all && !this.dom)?1:0; 
    this.ns5=(this.dom && parseInt(this.ver) >= 5) ?1:0; 
 
    this.ns4=(document.layers && !this.dom)?1:0; 
    this.bw=(this.ie5 || this.ie4 || this.ns4 || this.ns5) 
    return this 
} 
bw=new verifyCompatibleBrowser() 
 
 
var speed=50;
 
var loop, timer ;
 
function ConstructObject(obj,nest){ 
    nest=(!nest) ? '':'document.'+nest+'.' 
    this.el=bw.dom?document.getElementById(obj):bw.ie4?document.all[obj]:bw.ns4?eval(nest+'document.'+obj):0; 
    this.css=bw.dom?document.getElementById(obj).style:bw.ie4?document.all[obj].style:bw.ns4?eval(nest+'document.'+obj):0; 
    this.scrollHeight=bw.ns4?this.css.document.height:this.el.offsetHeight 
    this.clipHeight=bw.ns4?this.css.clip.height:this.el.offsetHeight 
    this.up=MoveAreaUp;this.down=MoveAreaDown; 
    this.MoveArea=MoveArea; 
    this.x; 
    this.y; 
    this.obj = obj + "Object" 
    eval(this.obj + "=this") 
    return this 
} 
function MoveArea(x,y){ 
    this.x=x;this.y=y 
    this.css.left=this.x 
    this.css.top=this.y 
} 
 
function MoveAreaDown(move){ 
    if(this.y>-this.scrollHeight+objContainer.clipHeight){ 
    this.MoveArea(0,this.y-move)
    if(loop) setTimeout(this.obj+".down("+move+")",speed) 
    }
    update_scrollbar();
} 
function MoveAreaUp(move){ 
    if(this.y<0){ 
    this.MoveArea(0,this.y-move) 
    if(loop) setTimeout(this.obj+".up("+move+")",speed) 
    } 
    update_scrollbar();
} 
 
function PerformScroll(speed){ 
    if(initialised){ 
        loop=true; 
        if(speed>0) objScroller.down(speed) 
        else objScroller.up(speed) 
    } 
} 
 
function CeaseScroll(){ 
    loop=false 
    if(timer) clearTimeout(timer) 
} 
var initialised; 
function InitialiseScrollableArea(){ 
    objContainer=new ConstructObject('divContainer') ;
    objScroller=new ConstructObject('divContent','divContainer') ;
    objScroller.MoveArea(0,0) ;
    objContainer.css.visibility='visible' ;
    initialised=true; 

    if (document.getElementById("einde_tekst"))
    {objScroller.scrollHeight=document.getElementById("einde_tekst").offsetTop+20;}
	else {objScroller.scrollHeight=2000;}
    update_scrollbar();
}