我的servlet 为什么运行不了？

首先建立我的servlet类，如下
package SERVLET;import java.io.IOException;
import java.io.PrintWriter;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class MyfirstServlet extends HttpServlet {

public void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
PrintWriter out=response.getWriter();
out.print("<html><body>my first servlet!</body></html>");
out.flush();
}}
2、编译后在当前目录下生成了\SERVLET\MyfirstServlet.class；
3、我将整个SERVLET目录剪切到了我的电脑目录
C:\Program Files\Apache Software Foundation\Tomcat 6.0\webapps\ROOT\server\WEB-INF\classes里。4、修改web.xml文件如下：<?xml version="1.0" encoding="ISO-8859-1"?><web-app xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_5.xsd"
    version="2.5">  <display-name>Welcome to Tomcat</display-name>
  <description>
     Welcome to Tomcat
  </description>
<servlet>
    <servlet-name>MyfirstServlet</servlet-name>
    <servlet-class>SERVLET.MyfirstServlet</servlet-class>
  </servlet>  
  <servlet-mapping>
    <servlet-name>MyfirstServlet</servlet-name>
    <url-pattern>/MyfirstServlet</url-pattern>
  </servlet-mapping></web-app>5、最后运行tomcat在浏览器输入http://127.0.0.1:8888/server/MyfirstServlet
（我的端口已经改为8888）
结果显示HTTP Status 404 - /server/MyfirstServlet
type Status reportmessage /server/MyfirstServletdescription The requested resource (/server/MyfirstServlet) is not available.