Hi,
I got the solution now
Just look the api!!
public RequestDispatcher getRequestDispatcher(java.lang.String path)
...
The pathname must begin with a "/" and is interpreted as relative to the current context root. Use getContext to obtain a RequestDispatcher for resources in foreign contexts. This method returns null if the ServletContext cannot return a RequestDispatcher.
Then you go to see getContext:
This method allows servlets to gain access to the context for various parts of the server, and as needed obtain RequestDispatcher objects from the context. The given path must be begin with "/", is interpreted relative to the server's document root and is matched against the context roots of other web applications hosted on this container.
In a security conscious environment, the servlet container may return null for a given URL.
These are all in the api ...
jack