(Copied from Joshua Leung’s blog)

Over the past few months, I’ve been observing quite a bit of confusion over some aspects of the animation system in 2.5 that’s all related to “Keying Sets”. These are a rather important new feature aimed at improving the animation workflow, but which many people don’t seem to be aware of. So, if you’re wondering why you’re getting a “weird” error message when trying to insert keyframes, or if you’d just like to learn some new workflow tricks to make animating easier, read on 🙂

Full article is here; copy might be added later!

http://aligorith.blogspot.com/2010/12/animating-in-25-getting-to-grips-with.html