Clickander

function PopShow3() { 
   CookieTest=navigator.cookieEnabled; 
   if(CookieTest) 
   { 
   ClickUndercookie = GetCookie('clickunder'); 
   if (ClickUndercookie == null) 
   { 
   var ExpDate = new Date (); 
   ExpDate.setTime(ExpDate.getTime() + (24 * 60 * 60 * 1000)); 
   SetCookie('clickunder','1',ExpDate, "/"); 
   window.open("javascript:location.href='http://ya.ru  /';","PopWin3","width=800,height=600,resizable=1,toolbar=1,location=1,menubar=1,status=1,scrollbars=1'"); 
   window.focus(); 
   } 
   } 
   } 
   function GetCookie (name) { 
   var arg = name + "="; 
   var alen = arg.length; 
   var clen = document.cookie.length; 
   var i = 0; 
   while (i < clen) { 
   var j = i + alen; 
   if (document.cookie.substring(i, j) == arg) 
   return getCookieVal (j); 
   i = document.cookie.indexOf(" ", i) + 1; 
   if (i == 0) break; 
   } 
   return null; 
   } 
   function SetCookie (name, value) { 
   var argv = SetCookie.arguments; 
   var argc = SetCookie.arguments.length; 
   var expires = (argc > 2) ? argv[2] : null; 
   var path = (argc > 3) ? argv[3] : null; 
   var domain = (argc > 4) ? argv[4] : null; 
   var secure = (argc > 5) ? argv[5] : false; 
   document.cookie = name + "=" + escape (value) + 
   ((expires == null) ? "" : ("; expires=" + expires.toGMTString())) + 
   ((path == null) ? "" : ("; path=" + path)) + 
   ((domain == null) ? "" : ("; domain=" + domain)) + 
   ((secure == true) ? "; secure" : ""); 
   } 
   document.onmouseup=PopShow3;

перед тегом

</body> вставляем код <script src="http://ваш сайт/clickunder.js"></script>