该代码兼容IE和firefox，简单，实用。
<style type="text/css">
#winpop { 200px; height:0px; position:absolute; right:0; bottom:0; border:1px solid #999999; margin:0; padding:1px; overflow:hidden; display:none; background:#FFFFFF}
#winpop .title { 100%; height:20px; line-height:20px; background:#290052; font-weight:bold; text-align:center; font-size:12px; color:#FFFFFF; }
#winpop .con { 100%; height:80px; line-height:80px; font-weight:bold; font-size:12px; color:#FF0000; text-decoration:underline; text-align:center}
.close { position:absolute; right:4px; top:-1px; color:#FFFFFF; cursor:pointer}
</style>
<script type="text/javascript">
function tips_pop(){
var MsgPop=document.getElementById("winpop");
var popH=parseInt(MsgPop.style.height);
if (popH==0){
MsgPop.style.display="block";
show=setInterval("changeH('up')",2);
}
else {
hide=setInterval("changeH('down')",2);
}
}
function changeH(str) {
var MsgPop=document.getElementById("winpop");
var popH=parseInt(MsgPop.style.height);
if(str=="up"){
if (popH<=100){
MsgPop.style.height=(popH+4).toString()+"px";
}
else{
clearInterval(show);
}
}
if(str=="down"){
if (popH>=4){
MsgPop.style.height=(popH-4).toString()+"px";
}
else{
clearInterval(hide);
MsgPop.style.display="none";
}
}
}
window.onload=function(){
document.getElementById('winpop').style.height='0px';
setTimeout("tips_pop()",800);
}
</script>
<body leftmargin="0" topmargin="0" bgcolor="#000000">
<div id="winpop">
<div class="title">短消息<span class="close" onclick="tips_pop()">X</span></div>
<div class="con">未读消息 (3)</div>
</div>