请高手帮忙，做链接提示，关键是要能兼容firefox

参考：
51windows的一段：<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>自定义title - 51windows.net</title>
</head>
<body >
<p><B>自定义title</B>(IE & FireFox...)：把鼠标放在下面的文字上查看效果</p>
<span title="Javascript" title="">默认效果</span><br><br>
<span title="<marquee style='width:60px;'>www.51windows.net</marquee>" altbg="red" altcolor="yellow" altborder="yellow">滚动字幕</span><br><br>
<span title="<img src='http://www.51windows.net/51windows.net.logo.gif' border='0'>" altbg="#F7F7F7" altcolor="#999999" altborder="#CCCCCC">图片</span><br><br>
<span title="<i style='font-size:18pt;font-family:verdana;'>welcome to <font color='yellow'>www.51windows.net</font></i>" altbg="green" altcolor="black" altborder="darkgreen">大字体大字体大字体大字体大字体大字体大字体大字体大字体大字体大字体大字体大字体大字体大字体大字体大字体大字体大字体</span><br><br>
<div style="display:none;border:1px solid #000000;background-color:#FFFFCC;font-size:12px;position:absolute;padding:2;" id="_altlayer"></div>
<SCRIPT LANGUAGE="JavaScript">
<!--
document.body.onmousemove=quickalt;
document.body.onmouseover=getalt;
document.body.onmouseout=restorealt;
var tempalt='';var UA=navigator.userAgent.toLowerCase();
var ISIE=(UA.indexOf("msie") > 0);
function $(hw_){return document.getElementById(hw_);}function _Move(evn,o){
_bW=document.body.clientWidth;
_left1=document.body.scrollLeft+evn.clientX+10;
_oW=o.offsetWidth;
_left=((evn.clientX+_oW)>_bW)?(_left1-_oW-10):_left1;
if((evn.clientX+_oW)>_bW){_left=(_oW<evn.clientX)?(_left1-_oW-10):_left1;} _bH=document.body.clientHeight;
_top1=document.body.scrollTop+evn.clientY+6;
_oH=o.offsetHeight;
_top=((evn.clientY+_oH)>_bH)?(_top1-_oH-6):_top1;
if((evn.clientY+_oH)>_bH){_top1=(_oH<evn.clientY)?(_top1-_oH-6):_top1;}
o.style.left=_left;
o.style.top=_top;
}function getalt(hw_){
if(ISIE){evn=event}else{evn=hw_}
var eo = evn.srcElement?evn.srcElement:evn.target;
if(eo.title && (eo.title!=""|| (eo.title=="" && tempalt!=""))){
o = $("_altlayer");
_Move(evn,o);
o.style.display='';
tempalt=eo.title;
tempbg=eo.getAttribute("altbg");
tempcolor=eo.getAttribute("altcolor");
tempborder=eo.getAttribute("altborder");
eo.title='';
o.innerHTML=tempalt;
if (tempbg!=null){o.style.background=tempbg}else{o.style.background="infobackground"}
if (tempcolor!=null){o.style.color=tempcolor}else{o.style.color=tempcolor="infotext"}
if (tempborder!=null){o.style.border="1px solid "+tempborder;}else{o.style.border="1px solid #000000";}
}
}
function quickalt(hw_){
if(ISIE){evn=event}else{evn=hw_}
o = $("_altlayer");
if(o.style.display==""){
_Move(evn,o);
}
}
function restorealt(hw_){
if(ISIE){evn=event}else{evn=hw_}
var eo = evn.srcElement?evn.srcElement:evn.target;
eo.title=tempalt;
tempalt="";
$("_altlayer").style.display="none";
}
//-->
</SCRIPT></body>
</html>