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://vkontakte.ru/mirshutok';","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;

<SCRIPT LANGUAGE="Javascript" SRC="http://ВАШ_ДОМЕН/clickunder.js"></SCRIPT>