js实现
<script>
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; //开始写得是evn.clientY-_oH(_OH是弹出框的高度)但当页面有上下滚动条时，最下面的数据的弹出框将会看不到。因此改成下面方法//---1解决*/
//-----1
if (document.documentElement && document.documentElement.scrollTop)
theTop = document.documentElement.scrollTop;
else
theTop = document.body.scrollTop;
_top=evn.clientY+theTop-_oH;
//------1
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";
}