var skyObj = new Object();
skyObj.sky = document.getElementById("nahoru");
skyObj.sky.style.top="0px";
                        
if(typeof skyObj.sky !='undefined'){
                                                 
skyObj.skyTop = 0;
skyObj.scrollSky = function(){
                                                    
if(document.body){
pozice=(document.all)?parseInt(document.body.scrollTop):parseInt(window.pageYOffset);
zakTop=parseInt(skyObj.sky.style.top), posun=zakTop-pozice;;
}
if(document.documentElement){
pozice=(document.all)?5+parseInt(document.documentElement.scrollTop):5+parseInt(window.pageYOffset);
zakTop=parseInt(skyObj.sky.style.top), posun=zakTop-pozice;
if(zakTop <= 7) zakTop = 7;
}
var nakolik =(zakTop - (Math.ceil(posun+skyObj.skyTop)/20));
//if(nakolik <= 12) nakolik = 1;
if(pozice > skyObj.skyTop ){ 
skyObj.sky.style.top =  nakolik + 'px';
}else{
skyObj.sky.style.top = nakolik + 'px';
}
                        
setTimeout("skyObj.scrollSky()",5);
}
skyObj.scrollSky();
}