When I log onto Facebook via my iPhone 4, sometimes I go into the chap app. Now, usually when someone tries to talk to you on the chat, it will show just bring up their name and conversation but sometimes my phone will vibrate and the name of the person will come up but there isn'tt anything written? What does this mean? Does it mean they've poked me or something? Was just curious so thought I'd ask....all answers appreciated. Thank you please.