var currentpos,timer; 
function initialize() 
{timer=setInterval("scrollwindow()",40);} //setInterval用来按指定间隔时间调用函数即多少时间运行一次函数，40为时间间隔，单位是毫秒，越大滚屏速度越小
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