Friends List

I have a problem, i always see my friends offline, i were chatting with a friend but i see his offline. Then i try to delete him and readd, but nothing i were the same problem..then i try to delete all my friends except one (the onlyone that i can see nline) and then try to add the first one again, but nothing change. I've seen a difference betwen this 2 friends, the one that i can see online have got 2 man near his nik, but the other fiend have just one and there is no a status [online] or [disconnected] .. how can i solve the problem? plz help me. ty