好像加个判断就可以 你试试
var offsetTop = float_banner.offsetTop;
window.onscroll = scroll_ad;
scrollTop = document.documentElement.scrollTop + document.body.scrollTop;
if(scrollTop != 0){
pos = scrollTop - float_banner.offsetTop;
}else{
pos = offsetTop - float_banner.offsetTop;
}
pos = pos / 10;
。。。