I go to a forum which uses vBulletin 3.8. When I log in, I use firebug to see what cookies were set. I see these cookies:
__utmb, __utmc, __utma, __ut
From http://en.wikipedia.org/wiki/HTTP_cookie:
Cookies are not directly visible to client-side programs such as JavaScript if they have been sent with the HttpOnly flag. From the point of view of the server, the only difference with respect of the normal case is that the set-cookie header line is added a new field containing the string `HttpOnly':
Set-Cookie: RMID=732423sdfs73242; expires=Fri, 31-Dec-2010 23:59:59 GMT; path=/; domain=.example.net; HttpOnlyWhen the browser receives such a cookie, it is supposed to use it as usual in the following HTTP exchanges, but not to make it visible to client-side scripts.
TheHttpOnlyflag is not part of any standard, and is not implemented in all browsers.
Update from 2017: a lot of time had passed since 2009, and HttpOnly header flag is became a standard, defined in the section 5.2.6 of RFC6265, with the storage semantics described in the same document (look for "http-only-flag" throughout the RFC text).
There is no way to access anything about the HttpOnly cookies from "non-HTTP" APIs, e.g. JavaScript. By design, neither reading, nor writing such cookies is possible.
Can use this extension for Uncheck HttpOnly, and then works document.cookie in javascript: https://chrome.google.com/webstore/detail/editthiscookie/fngmhnnpilhplaeedifhccceomclgfbg