as the others quite rightly pointed out you shouldn't use type as a
model name in Rails. However, I suspect the error you got wasn't
caused by this, but rather by the fact that you were trying to access:
instead of say:
if you look at your controller it will look something like:
@type = Type.find(params[:id])
params[:id] in your case will be nil (after all you did not specify
one, right?) so it will basically try to do Type.find(nil) if you fire
up the console, you'll see that this doesn't work.
This is an inelegance of how actions map to controllers, and once you
get better and start using map.resources this inelegance will be gone.
Just hang in there.
Also I really recommend you put down the Rolling with Rails article
and go out and buy the Agile Web Development With Rails (Second
Edition!) book. I remember that Rolling with Rails was the first
article about Rails I read. The interesting part is that at the time,
it was pretty much the ONLY article about Rails. Yes, this was almost
two years ago. So buy the book and save yourself some pain.