鼠标放到链接上出现一个说明框，里面有滚动的文字说明

<a href="http://www.helpor.net" target="_blank" onMouseOver="helpor_net_show(this,event,'看到了吧？')" onMouseOut="helpor_net_hide()">把鼠标放上来试试</a>
<div id="tooltip2" style="position:absolute;visibility:hidden;clip:rect(0 150 50 0);width:150px;background-color:seashell">
<layer name="nstip" width="1000px" bgColor="seashell"></layer>
</div>
<SCRIPT language="JavaScript">
<!--
if (!document.layers&&!document.all)
event="test"
function helpor_net_show(current,e,text)...{

if (document.all&&document.readyState=="complete")...{
document.all.tooltip2.innerHTML='<marquee style="border:1px solid #3399ff">'+text+'</marquee>'
document.all.tooltip2.style.pixelLeft=event.clientX+document.body.scrollLeft+10
document.all.tooltip2.style.pixelTop=event.clientY+document.body.scrollTop+10
document.all.tooltip2.style.visibility="visible"
}

else if (document.layers)...{
document.tooltip2.document.nstip.document.write('<b>'+text+'</b>')
document.tooltip2.document.nstip.document.close()
document.tooltip2.document.nstip.left=0
currentscroll=setInterval("scrolltip()",100)
document.tooltip2.left=e.pageX+10
document.tooltip2.top=e.pageY+10
document.tooltip2.visibility="show"
}
}
function helpor_net_hide()...{
if (document.all)
document.all.tooltip2.style.visibility="hidden"
else if (document.layers)...{
clearInterval(currentscroll)
document.tooltip2.visibility="hidden"
}
}

function scrolltip()...{
if (document.tooltip2.document.nstip.left>=-document.tooltip2.document.nstip.document.width)
document.tooltip2.document.nstip.left-=5
else
document.tooltip2.document.nstip.left=150
}
//-->
</SCRIPT>