Cookie Being Erased After Page End. Why?

I'm building a multi-langual site, and I want to store the language selected in a cookie. When the querystring contains a "lang" parameter, I'm changing the cookie's value. The valuese represent the language ID in my DB. When no var passed throgh the QueryString, and no cookie found, the system should put the value of the default language in the cookie.

The only problem is the cookie is being erased somehow after the only page I created so far is over. the page itself can access the cookie, but once it's processing is over, the cookie no more exists.

I have no idea why it happenes, nor how should I fix it. I've set the cookies("name").Expires = DateAdd("m", 1, Now()), and checked there is no other access to the cookie. But nada. the cookie still vanish every time.