gmail chat

I keep getting little chat windows popping up, not noticing them for a while (because I'm away from the computer or looking at a different window), replying eventually, and then getting the "so&so did not get your chat" message. I've never used chat, so how does the etiquitte of this work? Is it understood that you might not see their chat in time, or do people assume that you're blowing them off? I think I've managed to actually talk to someone once, out of perhaps 6 or 7... Meh.