First you have to do this:
$(document).ready(function () {
$('.close_i').click(function(){
$('.adsbox').hide();
$('.open_i').show();
$.cookie("Disclaimer", 1, { expires : 3 });
});
$('.open_i').click(function(){
$('.adsbox').show();
$('.open_i').hide();
$.removeCookie("Disclaimer");
});
});
If he closed the adds, whenever he enter the page again the adds must be closed (3 days from now on), so you have to add this also:
$(document).ready(function () {
if ($.cookie("Disclaimer")){
$('.adsbox').hide();
$('.open_i').show();
});
});