当鼠标移动上去，会出现一个浮动的层。这个效果怎么做？？

[CODE]
<form method="POST" name="from" action="">
<a style='CURSOR:hand' onmouseover='showmenu(event,"<img name=LogoPic onload=\"javascript:if(this.width>200)this.style.width=200;\">");document.images.LogoPic.src=document.from.Logo.value;' onmouseout='delayhidemenu()' >[预览]</a>
<div class="menuskin" id="popmenu" onmouseover="clearhidemenu();highlightmenu(event,'on')" onmouseout="highlightmenu(event,'off');dynamichide(event)" style="Z-index:100"></div>
<style>.menuskin {Border: #666666 1px solid; Visibility: hidden; Position: absolute; Font: 12px Verdana; Background-Color:#EFEFEF; background-repeat : repeat-y;}</style>
<input type="hidden" name="Logo" value="http://bbs.bc-cn.net/UploadFace/27761.jpg"></form>

<script language="javascript">
var menuOffX=0 //菜单距连接文字最左端距离
var menuOffY=18 //菜单距连接文字顶端距离
var fo_shadows=new Array()
var linkset=new Array()
////No need to edit beyond here
var ie4=document.all&&navigator.userAgent.indexOf("Opera")==-1
var ns6=document.getElementById&&!document.all
var ns4=document.layers
function openScript(url, width, height){
var Win = window.open(url,"openScript",'width=' + width + ',height=' + height + ',resizable=1,scrollbars=yes,menubar=no,status=no' );
}
function showmenu(e,vmenu,mod){
if (!document.all&&!document.getElementById&&!document.layers)
return
which=vmenu
clearhidemenu()
ie_clearshadow()
menuobj=ie4? document.all.popmenu : ns6? document.getElementById("popmenu") : ns4? document.popmenu : ""
menuobj.thestyle=(ie4||ns6)? menuobj.style : menuobj

if (ie4||ns6)
menuobj.innerHTML=which
else{
menuobj.document.write('<layer name=gui bgColor=#E6E6E6 width=165 onmouseover="clearhidemenu()" onmouseout="hidemenu()">'+which+'</layer>')
menuobj.document.close()
}
menuobj.contentwidth=(ie4||ns6)? menuobj.offsetWidth : menuobj.document.gui.document.width
menuobj.contentheight=(ie4||ns6)? menuobj.offsetHeight : menuobj.document.gui.document.height

eventX=ie4? event.clientX : ns6? e.clientX : e.x
eventY=ie4? event.clientY : ns6? e.clientY : e.y

var rightedge=ie4? document.body.clientWidth-eventX : window.innerWidth-eventX
var bottomedge=ie4? document.body.clientHeight-eventY : window.innerHeight-eventY
if (rightedge<menuobj.contentwidth)
menuobj.thestyle.left=ie4? document.body.scrollLeft+eventX-menuobj.contentwidth+menuOffX : ns6? window.pageXOffset+eventX-menuobj.contentwidth : eventX-menuobj.contentwidth
else
menuobj.thestyle.left=ie4? ie_x(event.srcElement)+menuOffX : ns6? window.pageXOffset+eventX : eventX

if (bottomedge<menuobj.contentheight&&mod!=0)
menuobj.thestyle.top=ie4? document.body.scrollTop+eventY-menuobj.contentheight-event.offsetY+menuOffY-23 : ns6? window.pageYOffset+eventY-menuobj.contentheight-10 : eventY-menuobj.contentheight
else
menuobj.thestyle.top=ie4? ie_y(event.srcElement)+menuOffY : ns6? window.pageYOffset+eventY+10 : eventY
menuobj.thestyle.visibility="visible"
ie_dropshadow(menuobj,"#999999",3)
return false
}
function ie_y(e){
var t=e.offsetTop;
while(e=e.offsetParent){
t+=e.offsetTop;
}
return t;
}
function ie_x(e){
var l=e.offsetLeft;
while(e=e.offsetParent){
l+=e.offsetLeft;
}
return l;
}
function ie_dropshadow(el, color, size)
{
var i;
for (i=size; i>0; i--)
{
var rect = document.createElement('div');
var rs = rect.style
rs.position = 'absolute';
rs.left = (el.style.posLeft + i) + 'px';
rs.top = (el.style.posTop + i) + 'px';
rs.width = el.offsetWidth + 'px';
rs.height = el.offsetHeight + 'px';
rs.zIndex = el.style.zIndex - i;
rs.backgroundColor = color;
var opacity = 1 - i / (i + 1);
rs.filter = 'alpha(opacity=' + (100 * opacity) + ')';
//el.insertAdjacentElement('afterEnd', rect);
fo_shadows[fo_shadows.length] = rect;
}
}
function ie_clearshadow()
{
for(var i=0;i<fo_shadows.length;i++)
{
if (fo_shadows[i])
fo_shadows[i].style.display="none"
}
fo_shadows=new Array();
}

function contains_ns6(a, b) {
while (b.parentNode)
if ((b = b.parentNode) == a)
return true;
return false;
}
function hidemenu(){
if (window.menuobj)
menuobj.thestyle.visibility=(ie4||ns6)? "hidden" : "hide"
ie_clearshadow()
}
function dynamichide(e){
if (ie4&&!menuobj.contains(e.toElement))
hidemenu()
else if (ns6&&e.currentTarget!= e.relatedTarget&& !contains_ns6(e.currentTarget, e.relatedTarget))
hidemenu()
}
function delayhidemenu(){
if (ie4||ns6||ns4)
delayhide=setTimeout("hidemenu()",500)
}
function clearhidemenu(){
if (window.delayhide)
clearTimeout(delayhide)
}
function highlightmenu(e,state){
if (document.all)
source_el=event.srcElement
else if (document.getElementById)
source_el=e.target
if (source_el.className=="menuitems"){
source_el.id=(state=="on")? "mouseoverstyle" : ""
}
else{
while(source_el.id!="popmenu"){
source_el=document.getElementById? source_el.parentNode : source_el.parentElement
if (source_el.className=="menuitems"){
source_el.id=(state=="on")? "mouseoverstyle" : ""
}
}
}
}
</script>[/CODE]

在想显示效果的图片附近做一个层，在层里写上想要提示的话或是插入图片，用鼠标选中图片，然后在Dreamweaver 的行为属性里找到“显示—隐藏层”选项，第一次选择“隐藏”选项，在列表中会出现“onLoad 显示—隐藏层”，再做一次上面的操作，但是这次选择“显示”选项，在列表中会出现“onLoad 显示—隐藏层”，将onload改为onMouseOver, 再做一次上面的操作，这次选择“隐藏”选项，在列表中会出现“onLoad 显示—隐藏层”，将onload改为onMouseOut, 你要的效果就出现了。