function scroll(o_kolik){
var novyTop=parseInt(document.getElementById("obsah").style.marginTop)-o_kolik;
if(-novyTop > maxP){
document.getElementById('obsah').style.marginTop="-"+maxP+"px";
prestan_rolovat();
}else if(-novyTop<0){
document.getElementById('obsah').style.marginTop="0px";
prestan_rolovat();
}else{
document.getElementById('obsah').style.marginTop=novyTop+"px";
}
}

function zacni_rolovat(o_kolik){
if(o_kolik>0){
o_kolik=o_kolik+2;
}else{o_kolik=o_kolik-2;}
scroll(o_kolik);
clearTimeout(roluje_se);
roluje_se=setTimeout("zacni_rolovat("+o_kolik+")",100);
}

function prestan_rolovat(){
clearTimeout(roluje_se);
}

function roluj_nahoru(){ 
zacni_rolovat(-10);
}  

function roluj_dolu(){ 
zacni_rolovat(10);
}

document.getElementById('obsah').style.marginTop="0px";
var puvodniH=400 //parseInt(document.getElementById("obsahU").style.height);
document.getElementById("obsah").style.height="auto";
var rolH=document.getElementById("obsah").offsetHeight;
document.getElementById("obsah").style.height=puvodniH;
var maxP=rolH-puvodniH;
var roluje_se;

document.getElementById("obsahU").style.overflow="hidden";
 var rn = document.createElement('a');
 rn.style.backgroundImage="url('rn.png')";
 rn.style.width="30px";
 rn.style.height="30px";
 rn.style.position="absolute";
 rn.style.right="70px";
 rn.style.top="220px";
 rn.href="javascript:roluj_nahoru();";      
 rn.onmouseover=function(){roluj_nahoru()};
 rn.onmouseout=function(){prestan_rolovat()};
document.getElementById("layout").appendChild(rn);

 var rd = document.createElement('a');
 rd.style.backgroundImage="url('rd.png')";
 rd.style.width="30px";
 rd.style.height="30px";
 rd.style.position="absolute";
 rd.style.right="70px";
 rd.style.top="610px";
 rd.href="javascript:roluj_dolu();";         
 rd.onmouseover=function(){roluj_dolu()};
 rd.onmouseout=function(){prestan_rolovat()};
document.getElementById("layout").appendChild(rd);

document.onkeydown=klavesa;

function klavesa(e){

var keycode;
if (window.event){keycode = window.event.keyCode;ctrl=window.event.ctrlKey;}
else if (e){keycode = e.which;ctrl=e.ctrlKey}
/*
if (keycode==13){
  scroll(20);
}
*/
}