I just finished explaining this to a client, and I've probably explained this a dozen times in the last few months to new Skinners, so here's an attempt to head off problems for some of the newer folk:
The naming of panes in DNN skins is important. The documentation and most tutorials or books say you MUST have a ContentPane. That's not exactly true, it's just that without one, you'll break DNN. The default location for DNN controls, especially admin controls, is the ContentPane. So if you do not have a pane named ContentPane, then you won't be able to admin your portal, login, or just about anything else useful, INCLUDING CHANGE THE SKIN.
But let's extend this a little further. The pane names ( the id="..." part of each tag ), for DNN's default skins, besides ContentPane, are TopPane, BottomPane, LeftPane and RightPane. When starting out skinning, stick to these names. Sure, you're going to put a Feedback module in the right pane, but don't name it FeedbackPane. First you might not always want the Feedback module and then it gets confusing, but more important to beginners is that it won't match the default DNN template you get on a basic install. If you name your panes differently, the modules in the default DNN template won't display. If you leave the names the same, the module content already exists in those panes and it's much easier to check what your new skin will look like.
You're going to run into enough skinning problems when you start out. So start by duplicating the existing working skins as much as possible. Then when you know a little more about what you're doing, and why to do it, branch off in your own direction. And by the way, if you're going to sell or give away your skins, keep the same naming conventions so you don't get innundated with support emails.
Hope it helps...
Jeff