tomcat启动出现的错误

2011-12-7 22:19:27 org.apache.catalina.core.AprLifecycleListener init
信息: Loaded APR based Apache Tomcat Native library 1.1.20.
2011-12-7 22:19:27 org.apache.catalina.core.AprLifecycleListener init
信息: APR capabilities: IPv6 [true], sendfile [true], accept filters [false], random [true].
2011-12-7 22:19:28 org.apache.coyote.http11.Http11AprProtocol init
信息: Initializing Coyote HTTP/1.1 on http-8080
2011-12-7 22:19:28 org.apache.coyote.ajp.AjpAprProtocol init
信息: Initializing Coyote AJP/1.3 on ajp-8009
2011-12-7 22:19:28 org.apache.catalina.startup.Catalina load
信息: Initialization processed in 705 ms
2011-12-7 22:19:28 org.apache.catalina.core.StandardService start
信息: Starting service Catalina
2011-12-7 22:19:28 org.apache.catalina.core.StandardEngine start
信息: Starting Servlet Engine: Apache Tomcat/6.0.33
2011-12-7 22:19:28 org.apache.catalina.startup.HostConfig deployDescriptor
信息: Deploying configuration descriptor host-manager.xml
2011-12-7 22:19:28 org.apache.catalina.startup.HostConfig deployDescriptor
信息: Deploying configuration descriptor manager.xml
2011-12-7 22:19:28 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory docs
2011-12-7 22:19:28 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory examples
2011-12-7 22:19:28 org.apache.catalina.core.ApplicationContext log
信息: ContextListener: contextInitialized()
2011-12-7 22:19:28 org.apache.catalina.core.ApplicationContext log
信息: SessionListener: contextInitialized()
2011-12-7 22:19:28 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory JSP
2011-12-7 22:19:29 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory msgBoard
2011-12-7 22:19:29 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory ROOT
2011-12-7 22:19:29 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory tag
2011-12-7 22:19:29 org.apache.catalina.core.StandardContext listenerStart
严重: Error configuring application listener of class 
java.lang.ClassNotFoundException: 
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1680)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1526)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4149)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4705)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:799)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:779)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:601)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1079)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:1002)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:506)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1317)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:324)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:142)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1065)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:840)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1057)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:463)
at org.apache.catalina.core.StandardService.start(StandardService.java:525)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:754)
at org.apache.catalina.startup.Catalina.start(Catalina.java:595)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
2011-12-7 22:19:29 org.apache.catalina.core.StandardContext listenerStart
严重: Skipped installing application listeners due to previous error(s)
2011-12-7 22:19:29 org.apache.catalina.core.StandardContext start
严重: Error listenerStart
2011-12-7 22:19:29 org.apache.catalina.core.StandardContext start
严重: Context [/tag] startup failed due to previous errors
2011-12-7 22:19:29 org.apache.coyote.http11.Http11AprProtocol start
信息: Starting Coyote HTTP/1.1 on http-8080
2011-12-7 22:19:29 org.apache.coyote.ajp.AjpAprProtocol start
信息: Starting Coyote AJP/1.3 on ajp-8009
2011-12-7 22:19:29 org.apache.catalina.startup.Catalina start
信息: Server startup in 1532 ms
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如何处理？