我最近用Myecplise做struts的时候碰到一个问题：我的web.mxl文件是这样的：
<?xml version= 1.0 encoding= UTF-8 ?>
<web-app xmlns= http://java.sun.com/xml/ns/j2ee xmlns:xsi= http://www.w3.org/2001/XMLSchema-instance version= 2.4 xsi:schemaLocation= http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd >
<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>



运行的的提示错误是：
Starting service Tomcat-Standalone
Apache Tomcat/4.0.6
PARSE error at line 2 column -1
org.xml.sax.SAXParseException: 组件类型“web-app”未被声明。
Starting service Tomcat-Apache
Apache Tomcat/4.0.6
有没有谁知道这是为什么啊？