If your talking about Yahoo messenger, it means your friend isn't literelly signed into Yahoo IM, but his mobile number is registered with Yahoo IM. U can send him IMs as you normally do, he will recieve them on his cell phone in the form of a text message. - i just want to warn you, sometimes when a 'mobile' person replies to your message, it doesn't go through, its not SUPPOSED to fail, but it does sometimes, so he is probably getting your messages just for some reason, can't reply -
