Java EE (Java Enterprise Edition) General Discussion

My applications are not reading web.xml file created by me. e.g. if i use servlet mapping for servlet HelloWorld
<servlet>
<servelt-name>HelloWorld</servlet-name>
<servlet-class>HelloWorld</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloWorld</servlet-name>
<url-pattern>Hello</url-pattern>
</servlet-mapping>

If i type url http://localhost/appname/servlet/HelloWorld, it works fine.
If i type http://localhost/appname/Hello it shows error. I haven't turned off default behaviour of Tomcat. Can somebody suggest me how to turn off default behaviour of Tomcat. In Anticipation.