Hello Lulai,

You can add a disclaimer with this solution :

Open : template/header.tpl
Search : <script language=JavaScript src={$baseurl}/js/myjavascript.js></script>
After Add : <script language=JavaScript src={$baseurl}/js/avert.js></script>

Create a .JS file into the /js folder. with this name : advert.js
( your domain /js/advert.js )

Place this script on you server and don't miss to change the text because it is in french and dedicated to the Adults contents :
Code:
<!--
function ScanCookie(variable)
   {
    cook = document.cookie;
    variable += "=";
    place = cook.indexOf(variable,0);
    if (place <= -1)
        return("0" );
    else
       {
        end = cook.indexOf(";",place)
        if (end <= -1) return(unescape(cook.substring(place+variable.length,cook.length)));
        else return(unescape(cook.substring(place+variable.length,end)));
       }
   }
function CreationCookie(nom,valeur,permanent)
   {
    if(permanent)
       {
        dateExp = new Date(2020,11,11);
        dateExp = dateExp.toGMTString();
            ifpermanent = '; expires=' + dateExp + ';';
       }
    else
        ifpermanent = '';
    document.cookie = nom + '=' + escape(valeur) + ifpermanent;
   }
if(ScanCookie("dejapopup" )==0)
   {
    var msg="ATTENTION : SITE PORNOGRAPHIQUE RESERVE AUX MAJEURS DE PLUS DE 18 ANS\n\nCe site Internet est réservé Ã* un public majeur et averti et est conforme Ã* toutes les réglementations en vigueur. Il contient des textes, des photos et des vidéos classées X qui peuvent être choquantes pour certaines sensibilités.\n\nCLIQUEZ SUR OK POUR CONTINUER,ANNULER POUR QUITTER..\n\n"
    if(confirm(msg))
        CreationCookie("dejapopup","oui",false)
    else
        window.location.replace('http://www.google.fr');
   }
//-->
You can see the result on http://www.videos-x-live.com

The script is activated on all you website because it is into the header.tpl file requested on all access to your website ;-)

Regards,
Georges