Try replacing your doctype tag with the following tag:

Code:
<web-app xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
Generally you don't need doctype in your web.xml, but you do need to say that it is a java 2ee web application.