httpSetCookie()

[vladimir]

I try to store some information received from user by using of httpSetCookie/httpGetCookie pair. The user's information will be used for    jobs filtration by name served by QUERY facility. For example, user is entering jobs section by follow link:
http://hostname:631/jobs/?key=filter,
there "filter" is filtering condition. In jobs.cgi module I do something like :
if(cgiGetVariable("key"))
    httpSetCookie(http,cgiGetVariable("key"));

and after that in cgiShowJObs():

cgiSetVariable("QUERY",key=httpGetCookie(http));

It is works, but only first time, so if user change section to Classes, for ex. and then come back - I can not receive any value of cookie.
Is httpSetCookie() really "set" cookie in browser or manipulate by HTTP fields only?