var lasty=0;
function show()
{
 
    var scrolltop=document.documentElement.scrollTop;
    var percent=0.1*(scrolltop-lasty);

    if(percent>0)
    {
    percent=Math.ceil(percent);
    }
    else
    {
    percent=Math.floor(percent);
    }
    
    lasty=lasty+percent;

    
}