ho scaricato questo script in rete e funziona benissimo oltre ad essere molto carino l'unico "difetto" e che si apre tutte le volte che carichi la pagina, e due giorni che provo a modificarlo in modo che si apri solo al primo accesso del vistatore, e se sto postando qui con esito negativo, qualche esperto saprebbe modificarmelo.

Grazie 1000
#fadeinbox{
position:absolute;
width: 500px;
left: 0;
top: -400px;
border: 1px solid black;
font-family:Verdana;
font-size:10; text-decoration:none;
background-color:rgb(255,204,0);
padding: 4px;
z-index: 100;
visibility:hidden;
}
</style>
<script type="text/javascript">
<!--

//Specify display mode. 3 possible values are:
//1) "always"- This makes the fade-in box load each time the page is displayed
//2) "oncepersession"- This uses cookies to display the fade-in box only once per browser session
//3) integer (ie: 5)- Finally, you can specify an integer to display the box randomly via a frequency of 1/integer...
// For example, 2 would display the box about (1/2) 50% of the time the page loads.

var displaymode="always"

var enablefade="yes" //("yes" to enable fade in effect, "no" to disable)
var autohidebox=["yes", 8] //Automatically hide box after x seconds? [yes/no, if_yes_hide_after_seconds]
var showonscroll="yes" //Should box remain visible even when user scrolls page? ("yes"/"no)
var IEfadelength=1 //fade in duration for IE, in seconds
var Mozfadedegree=0.05 //fade in degree for NS6+ (number between 0 and 1. Recommended max: 0.2)

////////No need to edit beyond here///////////

if (parseInt(displaymode)!=NaN)
var random_num=Math.floor(Math.random()*displaymode)
if(document.cookie.indexOf("fadedin=yes")!=-1){
function displayfadeinbox(){
var ie=document.all && !window.opera
var dom=document.getElementById
iebody=(document.compatMode=="CSS1Compat")? document.documentElement : document.body
objref=(dom)? document.getElementById("fadeinbox") : document.all.fadeinbox
var scroll_top=(ie)? iebody.scrollTop : window.pageYOffset
var docwidth=(ie)? iebody.clientWidth : window.innerWidth
docheight=(ie)? iebody.clientHeight: window.innerHeight
var objwidth=objref.offsetWidth
objheight=objref.offsetHeight
objref.style.left=docwidth/2-objwidth/2+"px"
objref.style.top=scroll_top+docheight/2-objheight/2+"px"

if (showonscroll=="yes")
showonscrollvar=setInterval("staticfadebox()", 50)

if (enablefade=="yes" && objref.filters){
objref.filters[0].duration=IEfadelength
objref.filters[0].Apply()
objref.filters[0].Play()
}
objref.style.visibility="visible"
if (objref.style.MozOpacity){
if (enablefade=="yes")
mozfadevar=setInterval("mozfadefx()", 90)
else{
objref.style.MozOpacity=1
controlledhidebox()
}
}
else
controlledhidebox()
}
}
function mozfadefx(){
if (parseFloat(objref.style.MozOpacity)<1)
objref.style.MozOpacity=parseFloat(objref.style.Mo zOpacity)+Mozfadedegree
else{
clearInterval(mozfadevar)
controlledhidebox()
}
}

function staticfadebox(){
var ie=document.all && !window.opera
var scroll_top=(ie)? iebody.scrollTop : window.pageYOffset
objref.style.top=scroll_top+docheight/2-objheight/2+"px"
}

function hidefadebox(){
objref.style.visibility="hidden"
if (typeof showonscrollvar!="undefined")
clearInterval(showonscrollvar)
}

function controlledhidebox(){
if (autohidebox[0]=="yes"){
var delayvar=(enablefade=="yes" && objref.filters)? (autohidebox[1]+objref.filters[0].duration)*1800 : autohidebox[1]*1800
setTimeout("hidefadebox()", delayvar)
}
}

function initfunction(){
setTimeout("displayfadeinbox()", 100)
}

function get_cookie(Name) {
var search = Name + "="
var returnvalue = ""
if (document.cookie.length > 0) {
offset = document.cookie.indexOf(search)
if (offset != -1) {
offset += search.length
end = document.cookie.indexOf(";", offset)
if (end == -1)
end = document.cookie.length;
returnvalue=unescape(document.cookie.substring(off set, end))
}
}
return returnvalue;
}

if (displaymode=="oncepersession" && get_cookie("fadedin")=="" || displaymode=="always" || parseInt(displaymode)!=NaN && random_num==0){
if (window.addEventListener)
window.addEventListener("load", initfunction, false)
else if (window.attachEvent)
window.attachEvent("onload", initfunction)
else if (document.getElementById)
window.onload=initfunction
document.cookie="fadedin=yes"
}
//-->

</script>

<DIV id="fadeinbox" style="filterrogid:dXImageTransform.Microsoft.RandomDissolve(du ration=2) progid:dXImageTransform.Microsoft.Shadow(color=red ,direction=135) ; -moz-opacity:0">
[img]images/default_asp_smartbutton30739.gif[/img]


<font face="Verdana" size="1">Adass Emilia Romagna le da il benvenuto!

In questi giorni, stiamo facendo degli aggiornamenti nel sito. Ci scusiamo
sind'ora per eventuali disagi.

Nel ricordarle che il sito è in continua evoluzione la invitiamo a scriversi
alle nostre News Letter per rimanere aggiornato sulle novità.</font></p></font>
<div align="center">
chiudi
</div>
</div>