I would like to know why something doesn't work when it doesn't work.

I just started playing with Pivotal Tracker, and because I have no idea how the app works, I try to do something which is (to me) obvious, namely drag a story from the current iteration to the backlog. My complaint isn't that I can't drag stuff into the backlog; I kinda understand it now, and while it doesn't match my model, I can live with that. My problem is that there's no feedback as to why the operation failed. The drop just does nothing silently. I may be especially dumb, but I spent 10 minutes tweaking attributes on the story and then trying to drag it into the backlog, failing, and repeating and failing with no feedback whatsoever as to why what I was doing was wrong.

What I'd like is when I try to do something illegal or invalid, a notification somewhere that says, "hey, you tried to do something dumb. Here's a link that explains why it doesn't work that way." Or at least some feedback that says, "yeah, I noticed you tried to do something and it failed," as I spent the first few minutes wondering if it was just my browser's javascript implementation, and the drop wasn't even tried.