var px = 10;//mehr=schneller 
var timer; 
function scrollDenDiv(val){ 
clearTimeout(timer); 
d=document.getElementById('div_content') 
y=d.scrollTop; 
if(val==1)y-=px; 
if(val==2)y+=px; 
if(y<=d.scrollHeight-d.offsetHeight+px&&y>=0-px){ 
d.scrollTop=y; 
timer=setTimeout('scrollDenDiv('+val+')',50); 
} 
if(y<0||y>d.scrollHeight-d.offsetHeight){ 
clearTimeout(timer); 
} 
}