让一个DIV在页面右边并跟随滚动条移动

function getScroll() {
var top, left, width, height;
if (document.documentElement && document.documentElement.scrollTop) {
top = document.documentElement.scrollTop;
left = document.documentElement.scrollLeft;
width = document.documentElement.scrollWidth;
height = document.documentElement.scrollHeight;
}
else if (document.body) {
top = document.body.scrollTop;
left = document.body.scrollLeft;
width = document.body.scrollWidth;
height = document.body.scrollHeight;
}
return { top: top, left: left, width: width, height: height };
}
function scall(){
var v = getScroll();
//alert(v.top);
var e = document.getElementById("float_right");
e.style.top = ((v.top) + 50) + "px"; //纵滚动条离顶部距离 
}
window.onload = scall ;
window.onscroll = scall ;