Notice that every servlet has to be mapped there (war/WEB-INF/web.xml) - example like this:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
<web-app>
<!-- Servlets -->
<servlet>
<servlet-name>MyServlet</servlet-name>
<servlet-class>org.my.servlet.class</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>MyServlet</servlet-name>
<url-pattern>/folder/path</url-pattern>
</servlet-mapping>
<!-- Default page to serve -->
<welcome-file-list>
<welcome-file>myapp.html</welcome-file>
</welcome-file-list>
</web-app>
Hope that helps.