var currentpos,timer; 
function initialize() 
{timer=setInterval("scrollwindow()",8);} 
function sc(){clearInterval(timer); }
function scrollwindow() 
{currentpos=document.body.scrollTop; window.scroll(0,++currentpos); 
if (currentpos != document.body.scrollTop) sc();} 
document.onmousedown=sc
document.ondblclick=initialize