We got this error when we we put the jsp in wrong directory. Ideally it should be under the path which is set in HTML Root Directory under project properties in Jdeveloper.
For Jdeveloper 9i the path where we set the Html Root Directory is as follow:
Open project properties à Common à Input Paths
For Jdev11G it is : Open project properties Project à Source Paths à Web Application. I have not check for Jdev10G but I think the path would be same.