多浏览器支持的右下角浮动窗口

<script>
function $(id)
{
return document.getElementById(id);
}
var LoginUI = !!window.LoginUI || {};
LoginUI.getViewportWidth = function(){
var width=0;
if(document.documentElement && document.documentElement.clientWidth){
width=document.documentElement.clientWidth;}
else if(document.body && document.body.clientWidth){
width=document.body.clientWidth;}
else if(window.innerWidth){
width=window.innerWidth-18;}
return width;
}
LoginUI.getViewportHeight = function() {
var height=0;
if(window.innerHeight){
height=window.innerHeight-18;}
else if(document.documentElement&&document.documentElement.clientHeight){
height=document.documentElement.clientHeight;}
else if(document.body&&document.body.clientHeight){
height=document.body.clientHeight;}
return height;
}
LoginUI.getViewportScrollX = function(){
var scrollX=0;
if(document.documentElement&&document.documentElement.scrollLeft){
scrollX=document.documentElement.scrollLeft;}
else if(document.body&&document.body.scrollLeft){
scrollX=document.body.scrollLeft;}
else if(window.pageXOffset){
scrollX=window.pageXOffset;}
else if(window.scrollX){
scrollX=window.scrollX;}
return scrollX;
}
LoginUI.getViewportScrollY=function() {
var scrollY=0;
if(document.documentElement&&document.documentElement.scrollTop){
scrollY=document.documentElement.scrollTop;}
else if(document.body&&document.body.scrollTop){
scrollY=document.body.scrollTop;}
else if(window.pageYOffset){
scrollY=window.pageYOffset;}
else if(window.scrollY){
scrollY=window.scrollY;}
return scrollY;
}
function scrollMsgTip()
{
var t = LoginUI.getViewportHeight() + LoginUI.getViewportScrollY() - $("msgtip").offsetHeight;
$("msgtip").style.top = t + "px";
$("msgtip").style.left = LoginUI.getViewportWidth() + LoginUI.getViewportScrollX() - $("msgtip").offsetWidth + "px";
}
function scrollTip()
{
scrollMsgTip()
}
window.onload = window.onscroll = scrollTip;
</script>

<div style='position:absolute;top:0;left:0;width:300px;height:180px;border:3px double #AAA' id='msgtip'>dfddfdf</div>