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>

以上是js代码，下面是浮动的窗口

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