HTTP Status 404 - /servlet/AddBook

我运行时出现如下错误:请高手帮忙解决一下,,刚接触,,一点都不懂,,
HTTP Status 404 - /servlet/AddBook--------------------------------------------------------------------------------type Status reportmessage /servlet/AddBookdescription The requested resource (/servlet/AddBook) is not available.
--------------------------------------------------------------------------------Apache Tomcat/6.0.18我的html文件是个提交表单:
代码为:<form method="post" action="/servlet/AddBook">
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web.xml设置代码:
<?xml version="1.0" encoding="ISO-8859-1"?> 
<!DOCTYPE web-app 
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" 
"http://java.sun.com/dtd/web-app_2_3.dtd"> 
<web-app> 
<display-name>My Web Application</display-name> 
<description> 
A application for test. 
</description><servlet>
    <servlet-name>AddBook</servlet-name>
    <servlet-class>servlet.AddBook</servlet-class>
 </servlet>
 <servlet-mapping>
    <servlet-name>AddBook</servlet-name>
    <url-pattern>/AddBook</url-pattern>
   </servlet-mapping>
 
</web-app>
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AddBook.class已经放在E:\Apache-Tomcat\webapps\addbook\WEB-INF\classes\servlet下了.-------------------------------------------------------------------------------------------------