What other declaration?
I see a servlet called "Hello" which is in the servlet class "HelloWorld"
The servlet called "Hello" should be accessed using the url
pattern "/HelloServlet"
Possibly you are mixing up the Servlet class with the URL you have defined to access the servlet?
Also, I think Bear is hinting at the fact that your Servlet class (and for that matter all
java classes you right) needs to be in a package.