set browser id

hello

i wrote a program that post some data to a server. the server response only if the correct browser identification was transmitted - i think so is this realy possible that a server dont send information if no browser id available or the wrong one?
however please tell me how can i set the browser id? i use the webclient class:
WebClient wc = new WebClient();
wc.Headers.Add("Content-Type","application/x-www-form-urlencoded");

and so on...

i have a new keyword for my problem:
"user-agent". if i post information to the server i have to set the user-agent. how can i do this? any ideas?

ok, if no one want to answer i do it myself ;-)

Webclient wc = new Webclient();
wc.Headers.Add("User-Agent","Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624");