这个是什么原因啊？？

严重: Error loading WebappClassLoader
  delegate: false
  repositories:
    /WEB-INF/classes/
----------> Parent Classloader:
org.apache.catalina.loader.StandardClassLoader@179c285
 org.apache.struts.action.ActionServlet
java.lang.ClassNotFoundException: org.apache.struts.action.ActionServlet
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1358)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1204)
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1083)
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:981)
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4045)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4351)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
    at org.apache.catalina.core.StandardService.start(StandardService.java:516)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:566)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
2010-8-20 13:07:32 org.apache.catalina.core.StandardContext loadOnStartup
严重: Servlet /Struts1Test1 threw load() exception
java.lang.ClassNotFoundException: org.apache.struts.action.ActionServlet
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1358)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1204)
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1083)
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:981)
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4045)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4351)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
    at org.apache.catalina.core.StandardService.start(StandardService.java:516)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:566)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)

这个是我的配置...

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.

<web-app>

  <servlet>

    <servlet-name>action</servlet-name>

    <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>

    <init-param>

      <param-name>config</param-name>

      <param-value>/WEB-INF/struts-config.xml</param-value>

    </init-param>

    <init-param>

      <param-name>debug</param-name>

      <param-value>3</param-value>

    </init-param>

    <init-param>

      <param-name>detail</param-name>

      <param-value>3</param-value>

    </init-param>

    <load-on-startup>0</load-on-startup>

  </servlet>

  <servlet-mapping>

    <servlet-name>action</servlet-name>

    <url-pattern>*.do</url-pattern>

  </servlet-mapping>

</web-app>